GEAR-CUTTING MACHINERY 

COMPRISING 

A COMPLETE REVIEW OF CONTEMPORARY 

AMERICAN AND EUROPEAN 

PRACTICE 

TOGETHER WITH 

A LOGICAL CLASSIFICATION AND EXPLANATION 
OF THE PRINCIPLES INVOLVED 



BY 

RALPH E. FLANDERS 

ASSOCIATE EDITOR OF MAC 11 LYE RV 
AUTHOR OF BEVEL GEARING " 



FIRST EDITION 
FIRST THOUSAND 



NEW YORK 
JOHN WILEY & SONS 

London: CHAPJVLVN & HALL, Limited 

1909 



,ff 



Copyright, 1909, 

BY 

RALPH E. FLANDERS 



o^'t^m 



Stanbopc iPress 

F. H. CILSON COMPANY 
BOSTON. U.S.A. 



Cla. A. Nb. 

JULIO 1909 



PREFACE. 



The author undertakes, in this book, to present a com- 
plete review of the present state of the art in the field of 
gear-cutting machinery. He aims to illustrate and describe 
every important contemporary design, whether of American 
or European origin. The book deals with the underlying 
principles involved, and the general features of the mechan- 
isms described; it does not concern itself particularly with 
those details of construction which are common to all 
machine tools, of whatever type. The discussion is closely 
confined, also, to present clay machines and methods, refer- 
ences to earlier practice being made only in cases where that 
practice conceals the germ of possible future development. 

The arrangement of the subject matter follows the classi- 
fication set forth in the opening chapter. That is to say, 
the machines are described in the order determined — first, 
by the form of gear each is designed to cut; next, by the 
principle of action involved; next, by the method of oper- 
ation employed; then by the kind of mechanism used; and, 
finally, by the structural design of the machine. In every 
case particular stress is laid on the underlying principles 
on which the mechanism operates. 

The book is believed to be unique in the thoroughness 
with which it treats of a given form of machine tool. This 
thoroughness will be invaluable to the shop manager, fore- 
man or operator whose work requires him to keep fully in- 
formed as to developments in gear-cutting machinery. Great 
pains have been taken to explain in a simple but adequate 
way the underlying principles of the different mechanisms, 
and the ..intelligent machinist will have no difficulty in com- 
prehending them. The designer or manufacturer will find 



iv PREFACE. 

that the logical classification which has been followed is 
just what is needed to stimulate the mind to a systematic 
solution of the problems that arise in the inventing of new 
machines. He will be led to consider all possible modi- 
fications of the fundamental idea he is studying^ and will 
thus be enabled to arrive at the proper solution of his prob- 
lem by a sure and orderly method of procedure. The 
student of mechanism will find described in the following 
pages the finest examples of the application of kinematic 
laws to be found in any branch of machinery. The range of 
principles illustrated is wide, and the use made of them is 
ingenious. 

The author's thanks are due to the many manufacturers, 
both in this country and in Europe, who have so freely 
furnished him with the necessary photographs, blue-prints 
and information. It is certainly worthy of note that but 
two of the scores of firms approached refused to furnish the 
required material, and in neither case was the machine 
in question of particular importance. The main subject 
matter of this book first appeared serially in the columns 
of Machineri/. The author desires in this place to make 
acknowledgment of the kindness of the publishers of that 
journal in permitting the material to be collected in the 
present form. 

R. E F. 

New York City, May^ 1909. 



CONTENTS. 



CHAPTER I. 

PAGE 

Methods of forming the Teeth of Gears 1 

The Classification of Gear-Cutting Machinery 2 

Five Principles of Action 3 

Four Methods of Operation 10 



CHAPTER II. 

Machines for forming the Teeth of Spur Gears 14 

Machines using Formed Shaper or Planer Tools 15 

Standard Machine Tools and Attachments using Formed 

Milling Cutters 19 

Semi-automatic Machines using Formed Milling Cutters 22 

Automatic Machines using Formed Milling Cutters. — Gen- 
eral Principles of Design 25 

Milling Machine Type of Automatic Spur Gear Cutter 29 

The Orthodox Automatic Spur Gear Cutter 33 

Standard Type of Automatic Formed Cutter Machine for 

Heavy Work 47 

Machines for Heavy Work with Column Adjustable for 

Diameter 55 

Spur Gear Cutting Machines with L-Shaped Bed 58 

Precision Formed Cutter Machines 59 

The Formed Tool Principle applied to the Grinding or 

Abrasion Process 65 

The Templet Principle applied to cutting the Teeth of Spur 

Gears 66 



CHAPTER III. 

Machines for forming the Teeth of Spur Gears {Continued) . 69 

Molding-generating Machines working by Shaper Action ...... 69 

The Molding-generating Milling or Hobbing Machine and its 

Action , 77 

A Milling Machine Attachment for Hobbing Spur Gears ...... 80 

A Column-and-Knee Type Spur Gear Hobbing Machine 81 

Gear Hobbing Machines with Cutter Slide on Bed 83 

V 



VI CONTENTS. 

Machines for forming the Teeth of Spur Gears {Continued), page 

The Stamlard Form of Hobbing Machine 86 

Hobbing Machines with Adjustable Spindle Column 93 

Gear Hobbing Machines of Special Design . 96 

The Grinding or Abrasion Operation applied to the Molding- 
generating Process 99 



CHAPTER IV. 

Machines for cutting the Teeth of Internal Gears and 

Racks 104 

Machines and Attachments for cutting Internal Gears l)y the 

Formed Cutter Principle 104 

Cutting Internal Gears })y the Molding-generating Principle. . . 108 

Formed Tool Rack-cutting Attachments to Standard Machines 110 

Special Formed Tool Rack-cutting Machines 114 

The Molding-generating Method applied to Rack Cutting 126 



CHAPTER V. 

Machines for cutting the Teeth of Worms and Helical 

Gears 129 

Machines using Formed Tools in a Shaping or Planing Operation 130 

Standard Machine Tools using Formed Milling Cutters 135 

Specialized Forms of Milling Machines for cutting Spirals by 

the Formed Cutter Method 142 

Specialized Formed Cutter Machine for Herringbone Gears.. . 151 
Automatic Machines for Milling Helical Gears v.nth Formed 

Cutters 151 

Molding-generating Principle for cutting Helical Gears. — 

Planing Operations 154 

The Hobbing Modification of the Molding-generating Princi- 
ple for cutting Helical Gears 159 

Hobbing Machines with Cutter Slide on Bed 163 

Hobbing Machines of Special Types 171 

The Field of the Hobbing Process for cutting Helical and 
Herringbone Gears 180 



CHAPTER VI. 

Worm-wheel Cutting Machines 182 

Gashing Worm-wheels by the Formed Cutter Process 184 

The Molding-generating or Hobbing Process 186 

Hobbing Worm-wheels in the Milling Machine 188 

Hobbing Worm-wheels in Machines designed for cutting 

other Forms of Gearing 191 



CONTENTS. vii 

Worm-wheel Cutting Machines {Continued). pace 
The Fly-tool and Taper Hob Methods of cutting Worm- 
wheel Teeth , 1!)G 

Machines and Attachments for cutting Worm-wheels by the 

Fly-tool or Taper Hob Method 201 

Cutting Wheels for Multiple Threaded Worms by the Fly- 
tool Process 214 

The Various Methods Compared 215 

The Manufacture of Hindley Worm Gearing 216 

CHAPTER VII. 

Machines for forming the Teeth of Bevel Gears 221 

Five Principles of Action 224 

Four Methods of Operation 228 

Machines using Formed Milling Cutters for Shaping the Teeth 

of Bevel Gears 232 

Attachments for forming the Teeth of Bevel Gears by the Temp- 
let Principle 242 

Machines for shaping or planing the Teeth of Bevel Gears by 

the Templet Principle 248 

A Machine for milling the Teeth of Bevel Gears by the Templet 

Principle 261 

Machines employing the Templet Principle for grinding the 

Teeth of Bevel Gears 266 

Machines Working on the Odontographic Principle for cutting 
the Teeth of Bevel Gears 267 



CHAPTER VIII. 

Machines FOR FORMING the Teeth OF Bevel Gears {Continued) 275 

Finishing Bevel Gears by the Operation of Impression 275 

Machines operating on the Molding-generating Principle, and 

employing the Planing or Shaping Operation 278 

Milling the Teeth of Bevel Gears on the Molding-generating 

Principle 296 

Bevel Gear Cutting Machines using a Hob and operating on 

the Molding-generating Principle 301 

Comparison of Molding-generating Machines for Bevel Gears. . 313 

Conclusion 314 



GEAR-CUTTING MACHINERY. 



CHAPTER I. 

METHODS OF FORMING THE TEETH OF GEARS. 

There is no form of machine tool which has called for 
more ingenuity in design than the gear-cutting machine. 
The methods by which gears may be cut are so numerous, 
the requirements are so varied, the possible application of 
ingenious geometrical principles through the mechanism 
used are so nearly limitless, that a wonderful variety in 
design and construction has been evolved, affording a field 
of stutly which is unparalleled in its interest to the mechanic 
and engineer. 

The earhest form of gear-cutting machinery to attain 
anything like its present state of development was the 
automatic spur gear machine using a milled cutter to shape 
the tooth. Later came a period in which various forms 
of bevel gear cutting machinery were evolved, the demand 
being stimulated by the necessities of the chainless bicycle 
business. More recently the requirements of the automo- 
bile have resulted in another period of inventive activity, 
which has resulted in the development of new machines 
and processes for gears of all kinds, though the bulk of the 
attention has been given to the spur and bevel forms. 

In the following pages the author has attempted to 
cover the whole field of gear cutting, illustrating, so far as 
possible, every machine and process which has come into 
commercial use, including at the same time some which 

1 



2 GEAR-CUTTING MACHINERY. 

have been built and used successfully, but which have not, 
for one reason or another, been placed on the market. Some 
of these machines are old, some of them new, some of them 
simple, some of them comphcated. Some of them are used 
for the finest kind of work, such as is required in watch and 
instrument gearing, while one of them will cut gears up to 
40 feet in diameter. The reader will see as we proceed 
that all these widely varying tools may be brought into 
a definite classification which links them all into one large 
family — the old and new, simple and complicated, large 
and small — by characteristics which are common to the 
different groups. 

The Classification of Gear-cutting Machinery. 

Gear-cutting machinery may be classified, first, accord- 
ing to its product. There are four main divisions in this 
classification, separating from each other the machines 
designed for cutting spur, spiral, bevel, and worm gearing, 
respectively. The cutting of internal gears and racks is 
analogous to the cutting of spur gears, and is included 
with it. Twisted or herringbone gears having parallel 
axes are in general cut in the same way as spiral gears, 
though, as gears, they belong to a different class. Some 
machines are so designed as to be capable of cutting more 
than one form of gear, but it is only done by making cer- 
tain adjustments or using certain attachments which, for 
the time being, convert them into machines of other types. 
The best example of a machine which covers all the divi- 
sions of this classification is the universal miller, which may 
be arranged to cut the teeth in any one of the four forms 
mentioned. 

The second classification of gear-cutting machinery 
depends on the principle of action involved. The five 
methods we will consider are: the formed tool, templet, 



FORMING THE TEETH OF GEARS. 3 

odontographic, describing-generating, and molding-gener- 
ating methods. This classification relates particularly to 
the way in which the tool is held and guided with refer- 
ence to the work, to produce the desired form for the 
tooth surfaces. 

The third method of classification relates to the nature 
of the operation. The four operations we will consider 
are: forming the tooth by impression, by planing or 
shaping, by milhng, and by grinding or abrasion. 

In studying the various combinations possible in these 
three different classifications it will be simplest to first 
consider the matter of cutting the teeth of spur gearing, 
investigating the principle of action involved, and the nature 
of the operation performed, in the different methods. 
From that we will be able to proceed to the appHcation 
of these principles and operations to the spur, bevel, and 
worm forms of gearing. 

Five Principles of Action. 

The Formed Tool Principle: This, the simplest and most 
obvious way of forming a gear tooth, is illustrated in 
Fig. 1. The gear to be cut is held firmly on a work arbor 
which, in turn, is firmly supported in the machine, in such 
a way that it can be indexed (or rotated through an angu- 
lar distance corresponding to one tooth) from time to 
time as occasion requires. In the upper part of the cut 
is shown a planer or shaper tool-post, carrying a formed 
tool having outlines accurately corresponding to the shape 
of a space between two of the teeth it is desired to form. 
It is evident that this formed tool, when properly set and 
fastened in the tool-post of the planer or shaper, may be 
fed clown into the work to the proper depth, in which case 
it will reproduce its outline in the work. The work may 
then be indexed, and the operation repeated to form 



4 GEAR-CUTTING MACHINERY. 

another tooth space. With the work indexed in the cUrec- 
tion shown in the cut, four tooth spaces, or three com- 
plete teeth, have been formed. A formed niiUing cutter 
may be used instead of the planer or shaper tool. This is 
shown at work on the under side of the blank. It repro- 
duces its outUne in the work in the same way that the 




Fig. 1. The Formed Tool Principle of Action as exemplified by the 
Shaper Tool and the Milling C'utter. 



planer tool does, being rotated in the direction indicated 
and fed through the work at the same time. 

The Templet Principle: This method of cutting gears is 
shown in Fig. 2. As in the previous case, the work is lu^ld 
on the table of the shaper. A templet holder is also 
mounted on the shaper table, carrying a templet, having 
a surface formed to the exact outhne desired for the 



FORMING THE TEETH OF GEARS. 



finished tootli. The tool shcle is disconnected from the 
feed screw, and weighted so that it falls of its own accord. 
To its side is clamped the guide plate shown, whose hori- 
zontal lower edge bears on the templet. As the table of 
the shaper is fed to the right, it will be seen that the 
curved surface of the templet will raise the guide, the tool 
block, and the tool, in such a fashion that the desired 
outline will be reproduced on the gear tooth. The upper 




DIRECTION OF FEED OF SHAPER TABLE 



Fig. 2. The Templet Principle, as arranged to be applied to the Shaper. 

surfaces of teeth a, b, c, and d have been formed in turn in 
this way, the work being indexed for this purpose as in the 
previous case. With the primitive arrangement shown, it 
will be necessary to reverse the work in the arbor to form 
the other side of the teeth. Teeth d and e had their faces 
finished in this way, tooth d being thus completely formed. 
It will be seen that obtaining accurate teeth by this 
method requires, first, an accurate templet; second, accu- 
rate setting of the templet and tool in proper relation to 
each other; and third, a bearing surface on the guide of 



6 



GEAR-CUTTING MACHINERY. 



exactly the same shape as the cutting edge of the tool. 
The guide plate is, of course, wide enough to bear on the 
templet for the full stroke of the ram. As shown, the 
gear to be cut has had the tooth spaces roughed out to 
shape, so that the finishing operation removes a compara- 
tively small amount of metal. 




FEED WORM 



SHAPER TABLE 



Fig. 3. The Odontographic Principle, which approximately outlines 
the Tooth Form by Mechanical Means. 



The Odontographic Principle: In shaping teeth by the 
odontographic principle, the tool is guided in some way 
by suitable mechanism to closely approximate the desired 
tooth outline by means of circular arcs, or other easily 
obtained curves. A simple example is shown in Fig. 3. 
The gear to be cut is held and indexed as in the two 
previous cases. The blank has had the teeth roughed out 
as in the previous case. The gear to be cut has involute 
teeth. With teeth of this form, in most cases a circular arc 



FORMING THE TEETH OF GEARS. 7 

may be found which will more or less closely approximate 
the true outline. Such a circular arc is shown at x y, with 
its center at o. The radius tool holder shown has its center 
at to agree with that of arc x y. The cutting point of 
the tool used is located on that arc. It will be seen from 
from this that when the radius tool is fed from position 
T^ to T^ by the feed worm, its point will follow the desired 
arc and cut the desired outhne for the tooth. By this 
means the upper surface of tooth a is formed. The same 
surfaces of teeth h, c, and d have previously been cut, as 
well as the opposite faces of d and e, tooth d being com- 
pleted. To cut the opposite faces, the work must be 
reversed on the arbor. 

The Describing-Generating Principle: This principle is 
shown in Fig. 4, applied to the shaping of involute teeth. 
The cutting of involute teeth only has been hitherto 
shown in these examples, owing to the fact that in other 
cases, as in this, it lends itself most readily to the pur- 
poses of illustration. The involute, as is well known, is 
the curve formed by a point in a cord which is being 
unwrapped from the periphery of a circle. In the illus- 
tration, the dotted line x y shows an involute generated 
in this fashion from the base circle shown. This base cir- 
cle is formed by the periphery of the rolHng disk, which is 
rigidly connected with the gear to be cut through the work 
arbor on which both are firmly mounted. Unlike the pre- 
vious cases considered, this work arbor is free to revolve 
on centers without being restrained by an indexing mech- 
anism; as in previous cases, the blank has had the teeth 
roughed out. The machine used is a shaper, as before. 
To some fixed part of the machine is clamped the tape 
holder shown. This has fastened to it two thin flexible 
metallic tapes, M^ and M^, the former stretched between 
screw S^ on the tape holder and the corresponding screw 



8 



GEAR-CUTTING MACHINERY. 



on the rolling disk, while the latter is similarly stretched 
between screws S^ and S^^. By this means, it will be seen 
that when the shaper table is fed in the direction indi- 
cated, the unwinding of M^ and the winding of M^ will 
roll the disk and the work with a positive motion. If 
now a tool be placed in the tool block of the shaper, hav- 
ing a cutting point set at the same height as the middle 



TOOL BLOCK 




DIRECTION OF FEED OF SHAPER TABLE 



Fig. 4. The Describing-Generating Principle, by which the Point of 
the Tool is constrained to follow the Desired Outline. 



thickness of the steel tapes, and if the table be fed as 
shown, the mechanism will constrain the tool point to cut 
an involute on the side of the tooth of the gear blank. 
^Vhen the tooth is at c, the tool will be at T^: when the 
tooth is at h, the tool, at T^, will have cut down about 
half the length of the face, as shown; when the tooth is 



FORMING THE TEETH OF GEARS. 9 

at a, its outline will have been completed on that side by 
the tool, at Ta. The way in which the involute is gener- 
ated will be easily understood when it is seen that the 
cutting point of the tool always coincides with a given 
point y in tape M^, so that the same involute as is gener- 
ated by this point in the unwinding tape is reproduced 
by the tool point. The device is incomplete, as shown, in 
that no provision is made for indexing. In this case the 
gear to be cut and the rolhng disk have. to be indexed 
with relation to each other, so as to present the different 
teeth properly for the tool to act upon them. At d is 
shown a completed tooth. 

The Molding-Generating Principle: This method of mak- 
ing gears depends on the fact that in a set of interchange- 
able gearing a gear formed correctly to run with one of the 
series will run with any of the series. The molding process 
consists in using a completed gear tooth or gear, of proper 
shape, to form other gears. Two examples of this are 
shown in Figs. 5 and 6. The first case supposes a forming 
gear, as shown, of correct shape. The blank to be formed 
is made of some plastic material like wax or clay. The 
blank and the forming gear are mounted on arbors at the 
proper distance apart, and rotated together at the proper 
speed ratio. The teeth of the forming gear, pressing into 
the plastic blank, will form spaces and press out teeth of 
the correct shape to mesh with itself, or with any other 
gear of the same interchangeable series. 

In Fig. 6 the blank is of metal or other non-plastic 
material, and the forming gear is replaced with a forming 
cutter having sharp edges of exactly the same outhne. 
The blank, which in this case is of the full outside diameter 
of the gear into which it is to be made, is rotated with the 
cutter as in Fig. 5. The cutter is reciprocated in the 
direction of its axis so as to take a series of cuts to form 



10 



GEAR-CUTTING MACHINERY. 



the tooth spaces as the rotation takes place. The prin- 
ciple is identical with that shown in Fig. 5. Of course, 




Fig. 5. The Molding-Genera- 
ting Principle applied to Roll- 
ing the Proper Form in a 
Plastic Blank. 



Fig. 6. The Same Principle em- 
ploying a Cutter having a Shap- 
ing Action, cutting Teeth in a 
Solid Blank. 



the cutter has to be fed directly in to the proper depth to 
start with, before the rotation commences. 

Four Methods of Operation. 

In classifying gear-cutting methods by the operations 
involved, we will take for the purpose of illustration the 
molding-generating method as apphed to the spur gear. 
Later on we will see how the same operations are applied 
to the cutting of other forms of gears by other methods. 
In the four cases shown in Figs. 7 to 10 the molding- 



FORMING THE TEETH OF GEARS. 11 

generating is done by a rack working in a gear, not by one 
gear working in another, as in Figs. 5 and 6. 

By Impression: Fig. 5 is an example of this kind, the 
teeth in the plastic blank being formed by the impression 
made by them on the forming gear. In Fig. 7 the same 
thing is shown, except that the forming member is a rack 
which has shaped the periphery of the gear with which it 
meshes into correct teeth, as shown. 

By Shaping or Planing: In Fig. 8 but one tooth space 
of the gear is formed at a time, and instead of using a 
rack to do the forming, a tool T^ may be used having an 
outline the shape of a rack tooth. This is fed along hori- 
zontally, and the gear to be cut is rotated in unison with 
it, the same way as in Fig. 7. If tool T^ is given a cutting 
movement in a shaper, the spaces formed will be of exactly 
the right shape and identical with those formed in the 
previous case. Each of the spaces will have to be formed 
in the same way, one after another, the work being indexed 
with reference to the imaginary rack, to bring the tool 
into proper position for each of them. Instead of form- 
ing both sides of a space at one operation, as with tool T^, 
a single side tool T^ may be used, corresponding with one 
side only of the rack. In this case one side only of each 
tooth is finished, so the tool or the work has to be reversed, 
after which the other sides are completed. 

By Milling: Instead of using a planer or shaper tool 
to match the side of the imaginary rack tooth, a milling 
cutter may be used, as shown in Fig. 9. In this case the 
gear is rotated, and the milling cutter advanced to agree 
\Yith the advance of the imaginary rack. The cutting face 
of the mill must of course be formed on a plane surface, as 
shown. This arrangement presents some difficulties when 
the gear to be cut has a wide face, since the circular mill 
will cut deeper into the tooth space at the center than it 



12 



GEAR-CUTTING MACHINERY. 



will toward the edges. This deepening of the tooth space 
at the center does not affect the acting tooth surface, and 
so is harmless (except possibly in the case of the genera- 
tion of pinions having a small number of teeth, and invo- 




Flg.9 
MILLING 



g.10 

GRINDING OR ABRASION 



Figs. 7, 8, 9 and 10. The Four Methods of Operation, as applied to 
the Molding-Generating Principle of Action. 



lute outUnes of low pressure angle, in which case the 
trouble due to interference is aggravated). The larger 
the diameter of the cutter as compared with the face of 
the gear, the less is the trouble on this score. 



FORMING THE TEETH OF GEARS. 13 

By Grinding or Abrasion: In Fig. 10 the milling cutter 
of Fig. 9 has been replaced by an emery wheel of similar 
shape, having a plane face perpendicular to the axis of the 
wheel spindle. The action on the work is identical with 
that in the previous case, subject only to the limitations 
of .the grinding process, such as the rapid wearing away 
of the material of the wheel, involving the necessity for 
constantly truing it up. Besides this, only a small amount 
of stock can be removed in a given time, as compared with 
the execution possible with a milling cutter. The process 
has the advantage that it can be used in hardened work. 

While the involute form of tooth has been used for illus- 
tration in Figs. 1 to 10 inclusive, all the various princi- 
ples and operations can be used for forming cycloidal and 
other forms of teeth also, though the mechanism and cut- 
ting tools are simplest and most effective as applied to 
cutting the involute shape. It should be understood, fur- 
thermore, that each of these various principles and oper- 
ations can be a})plied to helical, worm, and bevel gearing as 
well as to spur gearing; many of the possible combina- 
tions are impracticable, of course. The purpose of this 
Hmited preliminary discussion of methods is to assist in 
systematizing the study of the various machines illus- 
trated and described in the following pages, and thus 
make their construction more easily understood. 



CHAPTER II. 
MACHINERY FOR FORMING THE TEETH OF SPUR GEARS. 

As explained in the last chapter, spur gear teeth may 
be formed in any one of five ways — by the formed tool 
method, the templet method, the odontographic method, 
the describing-generating method, or the molding-gener- 
ating method. The extent to which these various schemes 
have been applied in practical use varies greatly. The 
formed tool method is at once the most obvious and the 
most used of them all. The templet principle has been 
applied to a limited extent, principally for gears of very 
large size. So far as the writer is aware, no practical 
appHcation of the odontographic principle has been made 
in the cutting of spur gears. The only machine that has 
come to his notice involving the describing-generating 
process was one invented by Mr. Ambrose Swasey and in 
use twenty years ago or more in the shops of the Pratt & 
\^Tiitney Company. This was not used, however, for mak- 
ing gear teeth, but for making gear tooth cutters, before the 
days of the formed cutter, which it was not adapted to 
making. The molding-generating process in various forms 
has received a wide application, second only to the formed 
tool method. 

The operations available for the formed tool method are : 
impression, shaping or planing, milling, and grinding or 
abrasion. Of these the impression process is obviously 
unsuited for practical work. The shaping or planing and 
the milling operations (particularly the latter) have a wide 
range of apphcation. In the case of the process of grinding 

14 



FORMING THE TEETH OF SPUR GEARS. 15 

or abrasion, but a single machine has ever been bui!t 
embodying the formed tool principle; so far as the writer 
is aware. 

Machines Using Formed Shaper or Planer Tools. 

The primitive application of the formed tool method is 
that in which a gear blank is mounted on index centers on 
the planer or shaper table, and has its teeth cut by a tool 
having an outhne corresponding to the desired tooth 
space. In this operation the tool is fed by hand to the 
proper depth and withdrawn. The work is then indexed 
for a second cut, the tool is fed down again, and the oper- 
ation is repeated until the gear is finished. This was 
shown diagrammatically in the upper part of Fig. 1. It is 
the simplest method of cutting a gear which has to be 
made immediately and for which formed milling cutters 
are not available. It also has its application in the case 
of gears of unusual size. Under these circumstances, how- 
ever, the machine used is generally a slotter instead of a 
planer or shaper. A formed tool is fastened in the tool- 
post of the machine, while the work is clamped to the 
revolving table. The indexing is done by such means as 
may be provided, usually a worm and worm gear or a 
master wheel. The Gleason and Newton templet machines 
(see Figs. 48 and 49) also may be, and doubless often are, 
used in the same way. 

Figs. 11 and 12 show a machine using the formed tool 
with the shaper method of action. The machine is an 
interesting one in its details, and it would require consid- 
erable space to go into full particulars, so only a general 
description of it will be given. The mechanism is mounted 
on a circular column. The work arbor is carried by a 
slide, vertically adjustable to suit the diameter of the 
work, the adjustment being obtained by the crank handle 



16 



GEAR-CUTTING MACHINERY. 




Fig. U. The Pederson Formed Tool Gear Shaping Machine. 

shown at the front of the column. The feed and indcxino; 
movements for the work are controlled by cams on the 
shaft shown at the upper side of the work slide. The 
cam shaft is operated by an adjustable friction mechanism 



FORMING THE TEETH OF SPUR GEARS. 17 




Fig. 12. Rear View of the Pederson Machine. 

from the driving shaft. The feed cam, by suitable lever 
connections, forces the blank slowly down toward the 
cutters until the proper depth has been reached, when it 
allows the springs shown at the top of the column to 



18 GEAR-CUTTING MACHINERY. 

quickly return it, whereupon a cam at the left of the 
shaft trips the mechanism by which the work is in- 
dexed. The feeding cam then comes into action again — 
and so on until the work is completed. The depth of 
the feed given the work shde by the cam movement is 
varied by altering the position of the contact block by 
which the cam lever transmits the feeding movement to 
the slide. This is changed by the horizontal double-crank 
handle seen at the extreme top of the column. The index- 
ing is effected through an index worm-wheel and worm, 
operated through the change gears shown in Fig. 11, from 
the vertical shaft driven by the bevel gears and small 
pulley at the left of the base. This pulley, and conse- 
quently the indexing mechanism, runs at constant speed, 
irrespective of the main drive. Provision is made for 
stopping the action of the machine automatically when 
the required number of teeth have been cut. 

The cutter slide is driven by a back-geared crank move- 
ment, adjustable for length of stroke and for various 
numbers of strokes per minute. Two tools are used, one 
cutting on the forward, the other on the return stroke. 
These tools, as may be seen from Fig. 11, are mounted in 
a rocking holder, which is tipped to bring first one and 
then the other into action as the end of each stroke is 
reached. This tipping is effected by the rocking and 
locking cam at the left end of the cutter slide in Fig 11. 
This rocking and locking cam is connected with a slot 
cam near the right-hand end of the slide, this latter being 
operated by a pin near the crank end of the connecting- 
rod. As the connecting-rod passes the center, going in 
either direction, it operates the slot cam, which, through 
its connection with the rocking and locking cam, brings 
the desired one of the two blades into action. The one of 
these blades which has the heaviest of the cutting to do 



FORMING THE TEETH OF SPUR GEARS. 19 

is of a simple U-shape, forming the bottoms and fillets of 
the tooth spaces. The other one, which has a hghter cut, 
forms the curved faces of the teeth. 

Among the advantages claimed for this machine are 
rapidity of action and very low first cost. The cost of the 
cutters is also very moderate, being about one-fifth of that 
for formed milling cutters of the same pitch. These cutter 
blades are planed to shape, and may be ground on the face 
without change of contour. By means of special cutters 
straddling the teeth of the gear, provision is made for 
cutting pinions of few teeth and considerable under-cut. 
The British rights for this machine have been acquired by 
Vickers Sons and Maxim, who are manufacturing it at 
their works at Erith, Kent. 

Standard Machine Tools and Attachments Using 
Formed Milling Cutters. 

More gears are cut by formed milling cutters than in 
any other way. It is distinctly a commercially successful 
process. The cutting tools are comparatively inexpensive, 
and retain their shape until they are entirely ground 
away, which is only after the accomplishment of a sur- 
prising amount of work. 

The simplest way to use a formed cutter is in the mill- 
ing machine. In a milling machine provided with an 
indexing head no attachments are required for gears of 
moderate size and small pitch, and many thousands of them 
are cut with this simple equipment. For gears of larger 
diameter, though still of a pitch small enough so as to 
be within the range of the pulHng power of the spindle, 
the worm-wheel of the dividing head becomes too small to 
accurately index the wheel. Many of the milling machine 
makers provide indexing attachments suitable for doing 



20 



GEAR-CUTTING MACHINERY. 



work of greater diameter than is possible otherwise. In 
Fig. 13 is shown an equipment of this kind built by the 
Cincinnati Milhng Machine Company, Cincinnati, Ohio. 
The head and foot stocks are mounted on elevating blocks 
to extend their swing. When working on large diameters, 
the table is raised and the cut taken on the under side of 
the work. This brings the thrust due to the cut down 
nearer to the bearing surfaces which have to resist it, and 




Fig. 13. Attachments for cutting Gears of Large Diameter on 
Cincinnati Milling Machines. 



gives a steadier cutting action than would be the case if 
the work were lowered far enough to have the cutter act 
on the top of the blank. The indexing is done simply and 
directly by a plate with rows of holes, of numbers corre- 
sponding to the number of teeth it is desired to cut. This 
plate is of much greater diameter than the index worm of 
the regular spiral head, and so gives more accurate results. 
Another method of mounting large gear blanks in the 
milling machine is shown in Fig. 14. Here the work is 



FORMING THE TEETH OF SPUR GEARS. 21 

held on a horizontal face-plate, indexed by a worm wheel 
of large diameter concealed within the base of the attach- 
ment. The indexing is effected by a crank on the worm- 
shaft having an index pin entering holes in a stationary 
index plate, as in the regular milling machine dividing 
head. When using the device the vertical movement of 
the knee on the column is employed to feed the work up 
past the cutter. 




Fig. 14, Le Blond Circular Milling Attachment with Indexing 
Arrangement, used for cutting Large Spur Gears. 

An attachment of a different kind for cutting gears in 
the milling machine is shown in Fig. 15. Here we have 
an arrangement which is bolted on the milling machine 
table and connected with the dividing head. This attach- 
ment is driven fronj the counter-shaft by a special belt 
connection which serves to operate the feed and indexing 
of the work, the usual feed connections being disconnected. 
The device renders the milling machine automatic in all its 
actions. The table with the work on it is fed forward 



22 



GEAR-CUTTING MACHINERY. 



slowly until the cutter has passed through the work and 
formed the tooth space. The table and work are then 
rapidly returned, after which the work is indexed and 
again fed forward as before. These processes are repeated 
until the gear is finished. The milhng machine is thus 




Fig. 15. Attachment made by Ludwig Loewe & Co. for converting 
the Milling Machine into an Automatic Gear Cutter. 



made in effect an automatic gear cutter, capable of cutting 
bevel gears and clutches, as well as spur gears. This 
device is made by Ludwig Loewe & Co., Berlin, Germany. 



SpMI-AUTOMATIC MACHINES UsiNG FORMED MiLLING 

Cutters. 

Leaving the special use of the standard milling machine 
in this work, and coming to milhng machines sp(H'ially 
adapted to cutting gear teeth, we are met by a bewiklering 
variety of designs of varying degrees of ingenuity and 
interest. We will first consider the simpler forms of these 



FORMING THE TEETH OF SPUR GEARS. 



23 



specialized milling machines, or "gear-cutting machines/' 
as we may better call them. 

In the simpler forms the development from the milling 




Fig, 16. Newark Gear-Cutting Machine Company's Semi-automatic 
Machine for Small Work. 

machine consists principally in embodying the dividing 
mechanism as a part of the machine, instead of making it 
an attachment. The feed may be operated by hand, or it 
may be connected by belt or gearing with the spindle, so 



24 GEAR-CUTTING MACHINERY. 

as to be driven positively. In the latter case an auto- 
matic stop is provided for throwing the feed out when the 
cut is completed. In the automatic form of machine the 
indexing mechanism, as well, is operated by power, as is 
also the quick return of the feed; and the movements are 
made dependent on each other in such a way that the 
machine of itself feeds the cutter through the work, returns 
it when the cut has been completed, indexes the work, and 
repeats the cycle until the job is finished. 

An example of the semi-automatic form of the machine, 
made by the Newark Gear Cutting Machine Company, 
Newark, N. J., is shown in Fig. 16. The mechanism is 
quite simple and may be readily understood from the cut. 
The cutter spindle is carried on a slide which has an auto- 
matic feed, driven by the spiral gears and change gears 
shown, which may be set to give the desired rate. An 
automatic stop is provided for throwing out the power 
feed when the required length of cut has been taken. 
The slide then has to be run back by hand and the work 
indexed by hand, when the automatic feed is again thrown 
out. The work spindle is carried on a slide gibbed to the 
face of the column of the machine. This slide carries the 
indexing mechanism also, and an overhanging arm for 
supporting the outer end of the work arbor. The index- 
ing mechanism is of the same type as that illustrated in 
Fig. 17 and described later. Such tools are adapted to 
manufacturing in small quantities where unskilled labor 
is empjloyed. The machines are inexpensive, and the oper- 
atmg skill required is of a comparatively low order. 

Machines of similarly simple action, but for larger 
work, have been built from time to time by builders of 
special machinery as required by their customers. Of these 
the large Pratt and Whitney gear-cutting machine with 
L-shaped bed, is perhaps the best known. 



FORMING THE TEETH OF SPUR GEARS. 25 

Automatic Machines Using Formed Milling Cutters 
— General Principles of Design. 

The fact that we illustrate twenty-eight automatic 
formed cutter machines, built by twenty-three makers, is 
good evidence of the commercial position of this type. 
Much thought and experience has gone into the develop- 
ment of the automatic gear cutter. In selecting such a 
machine, important requirements to be looked out for are : 
accuracy of indexing, power and durabihty of the feed 
and cutter-driving mechanisms, rigidity of construction, 
convenience of handling, and range of usefulness. 

In the matter of accurate indexing (which is of prime 
importance, especially for gears which are to run at high 
speeds), the important considerations are the accuracy of 
the index worm-wheel and the mechanical construction of 
the indexing mechanism. With the exception of the 
machines shown in Figs. 19, 20, 43, 44, 45, and 46, which 
are for comparatively small work with small numbers of 
teeth, the principle of the indexing mechanism is the same 
for all of these machines. 

The work spindle has mounted on it (see Fig. 17) a 
worm-wheel driven by an indexing worm. This worm 
is connected by change gears A, B, C, and D with a shaft 
which is arranged (usually) to make one complete revolu- 
tion when the proper time for indexing arrives. The 
change gears are so set in connection with the invariable 
movement of the index shaft as to give the exact move- 
ment required to rotate the blank to the point where it is 
desired to cut the next tooth. In some machines pro- 
vision is made for giving two or four complete revolutions 
to the driving shafts when the number of teeth to be 
indexed is small. It is important that the mechanism by 
which this shaft is set in motion and stopped shall be 



26 



GEAR-CUTTING MACHINERY. 



very carefully designed, so that the stopping will always 
take place at exactly the same point in the rotation, 
thus permitting no over-running or under-running of the 
worm. 

In the construction of the worm-wheel there are two 
plans followed. Some makers, notably the Brown & Sharpe 
Manufacturing Company, prefer to make each worm-wheel 
an accurate copy of a master wheel which they know to be 
of unimpeachable accuracy. Other builders prefer to make 
each index wheel by itself, and generate each one to a high 



Index. Driving Shaft. -Makes one,two,or 
Other determined number of revolutions 
for each indexing. 




:^??S;y???^<^ 



Gears A,B,C and D are 
chosen to index the work 
for the required number 
of teeth . 



^D 




Index Worm 



Fig. 17. Diagram showing the arrangement of the Standard 
Indexing Mechanism. 



degree of perfection by methods well understood and com- 
monly employed in such work, generally involving mak- 
ing the rim in halves. 

In the matter of obtaining power and durability for the 
drive a variety of opinions will be found expressed in the 
various designs. Some of them have the spindles driven 
by spur gearing (or bevel gearing in some cases), while 
other makers prefer spiral or worm gear drives. There is 
much conflict of opinion as to the advantages of these 
various forms. In some cases the builder is restricted in 



FORMING THE TEETH OF SPUR GEARS. 



27 



his choice by structural features which hmit him to one 
form only. In any event the drive should be smooth and 
powerful. 

The capacity of gear-cutting machines for taking heavy 
chips may be easily allowed to fall below the limit of the 
driving power available at the spindle, if the frame of the 
machine and the design of gibbing of the various slides 
are such as to make the machine lacking in rigidity. The 
various requirements for doing w^ork rapidly and accu- 
rately may be understood from the rough sketch of a sec- 

Elevation of Center of Cutter alove Bcaiiiig, 

c 

No Bearing 



Holding-down Gi^ 




Width of Guiaing Surface 
-Width of Bearing Surface J 



Fig. 18. Cross-section through Cutter SHde of Typical Gear 
Cutter, ilhistrating Certain Principles relating to Accuracy 
and Cutting Power. 



tion through the spindle and cutter slide of a gear-cutting 
machine such as is shown in Fig. 18. This sketch does 
not represent any particular machine, but shows some 
features which are common to a number of makes; 
unnecessary details have been omitted. One of the 
requirements is that the strain of the cutting action shall 
be brought as close to the bearing surface as possible. 
This applies in the case of both the work spindle and the 
cutter spindle. It will be noted in Fig. 18 that the eleva- 
tion of the center of the cutter above the bearing is very 



28 GEAR-CUTTING MACHINERY. 

small, so that the irregular thrust of the cutting action 
when working at full capacity has httle effect in disturb- 
ing the rigidity of the machine. Bearing surfaces of great 
area are also advisable to give firmness to the structure. 
It will be noted that the bearing surface extends the full 
width of the bed of the machine in the sketch. With this 
wide bearing surface, however, provision should be made 
for guiding the slide for ahgnment, with much narrower 
surfaces, to prevent a cramping or ''bureau-d rawer'' 
action, as it has been called. The guiding in this case is 
done entirely by the comparatively narrow dovetail slide 
at the right. There is no side bearing at the left, a clear- 
ance space being provided at the right-hand edge of that 
slide as indicated. A strap is provided here, however, for 
holding the slide down on to its bearing, thus checking 
any lifting tendency at this point. It will be noted that 
the feed screw is placed quite close to the cutting point. 
This provision also tends toward smoothness and ease of 
action, since the power is then applied directly instead of 
in a way to cramp the slide on its bearings. The rigidity 
and smoothness which these provisions insure are of great 
importance in permitting the use of very heavy cuts and 
in lengthening the life of the cutter. 

In regard to these matters, and the matter of con- 
venience of operation as well, much can be surmised from 
a careful inspection of the illustrations of the various 
machines here shown. Instead of making invidious com- 
parisons in these particulars, it has been thought best to 
let the reader draw such conclusions as he can from the 
information given. The descriptions of the various auto- 
matic gear cutters will be found to contain explanations 
of their construction, and to refer to such particular points 
as may be peculiar to each case. To make comparisons 
easy, machines of similar type have been placed together 



FORMING THE TEETH OF SPUR GEARS. 29 

in regular order. Of course such of the good quahties in 
a machine tool as depend on accurate workmanship and 
the design of details not visible from the exterior will 
have to be judged by other means than a mere inspection 
of engravings. In the matter of accurate workmanship, 
particularly, the reputation of the builder will go a long 
way with the interested investigator. 

Milling Machine Type of Automatic Spur Gear Cutter. 

As has been stated, the automatic gear cutter is a 
specialized form of the milling machine. There are no 
machines in our list that show this more plainly than the 
two illustrated in Figs. 19 and 20. The first of these is 
built by the D wight Slate Machine Company, of Hartford, 
Conn. The machine at once shows itself to be a modified 
mining machine, with the usual screw feed replaced by 
a cam mechanism which gives a slow forward movement 
and a quick return. This is altered to give the proper 
length of feed, by means of the slotted link shown. The 
orthodox dividing head with worm and worm-wheel has 
been replaced by a dividing plate on the head-stock spindle, 
with notches to correspond with the number of teeth it 
is desired to cut. An automatic trip is provided which 
thro\vs out the feed at the completion of the last tooth. 
The various adjustments for different diameters of gears 
and lengths of cut will be readily understood from an 
inspection of the figure. This machine is also made 
in a style adapted to the cutting of bevel gears as well as 
spur gears. 

In the machine shown in Fig. 20, built by Sloan & Chace 
Manufacturing Company, Ltd., Newark, N. J., the feed is 
effected by a screw as in the ordinary milling machine, 
instead of by cams as in the previous case. The motion 



30 



GEAR-CUTTING MACHINERY. 



for the indexing and quick return is taken from the coun- 
ter-shaft by the pulley shown near the base of the machine 
at the left. This gives a constant speed at the highest 
practicable rate, whatever the spindle speed may be. The 




Fig. 19. The Dwight Slate Cam-actuated Automatic Gear Cutter. 



cutting feed is obtained from a connection with the spindle 
through a feed box, giving three changes. The indexing 
is ingeniously effected by the first half-turn of the feed 
screw, and is done positively without requiring the use^ of 
springs. A dial plate is used as in the previous case. 



FORMING THE TEETH OF SPUR GEARS, 



31 



The spindle head is adjustable in and out on the top of 
the column for centering the cutter. This machine shows 
the influence of the watch machinery maker's ideas applied 
to a machine of rather larger capacity than usual with such 




Fig. 20. The Sloan & Chace Automatic Gear Cutter for 
Small and Medium Size Work. 



construction. It is intended to embody the watchmaker's 
ideas of accuracy as well. 

Another machine that shows the hereditary influence of 
the miller is shown in Fig. 21. In this case, however, the 
relative positions of the work spindle and the cutter 
spindle have been reversed from that occupied in the 
mining machine or in the tools shown in the two pre- 



32 



GEAR-CUTTING MACHINERY. 



ceding cuts. The work spindle passes through the up- 
rights of the column, and carries a worm dividing gear at 
the rear end, while the cutter slide is located on the knee. 
In the position shown, with the intermediate quadrant 




Fig. 21. The Becker-Brainard Automatic Gear-Cuttina; Machine. 



elevated, the cut is being taken on an angle as woukl be 
required in cutting bevel gears, for which this machine is 
also adapted. For cutting spur gears the slide is horizon- 
tal. Change gears for dividing are seen at the rear of the 
column beneath the casing for the indexing wheel. The 



FORMING THE TEETH OF SPUR GEARS. 33 

indexing is done by a friction mechanism which is released 
at the proper time, coming up against a positive stop when 
one revolution has been made. The spindle driving and 
feed mechanisms are carried entirely by the knee. It will 
be noted that the gear driving the cutter spindle has heli- 
cal teeth. Where a cutter spindle is to be driven by spur 
gears this is a construction often followed, particularly in 
Europe, to give a smoother and more even motion than 
would be obtained by teeth cut straight across in the ordi- 
nary fashion. An incidental convenience of this machine 
is a trough just beneath the cutter spindle, enclosing a 
slowly moving spiral conveyor. The chips fall from the 
cutter into the trough, and are pushed out by the con- 
veyor over the edge of the knee into the pan base, away 
from the mechanism of the machine. This machine is 
built by the Becker Milling Machine Company, Hyde Park, 
Mass. 

The Orthodox Automatic Spur Gear Cutter. 

The automatic gear cutter of the conventional type, for 
small and medium-sized work, has the work and cutter 
spindles both horizontal, and arranged in the same rela- 
tion to each other as in the Becker-Brainard machine. 
Instead, however, of adjusting the machine for the diame- 
ter of work by raising or lowering the knee carrying the 
cutter spindle, the work arbor is raised or lowered, being 
carried for that purpose in a head vertically adjustable on 
a column at the end of the bed of the machine. The cut- 
ter slide when arranged for cutting spur gears only is 
gibbed directly to the top surface of the bed. 

One of the best known examples of this orthodox type 
of automatic gear-cutting machine is that built by the 
Brown & Sharpe Manufacturing Company, Providence, R. I. 
A front view of one of the smaller sizes is shown in Fig. 22. 



u 



GEAR-CUTTING MACHINERYo 



The spindle of this machine is driven by worm gearing 
which has the parts reversed from the order they would 
naturally take, since the worm-wheel is the driver, and 
the worm, which is much larger in diameter than the wheel, 
is the driven member. This arrangement gives the 




Fig. 22. An Example from the Brown & Sharpe Line of Automatic 

Gear Cutters. 



smopthness of drive of worm gearing, an enlarged bearing 
area, and the advantage of being able to shift the whole 
spindle with its driving gear endwise in adjusting the 
cutter centrally with the work, instead of requiring that 
the driving gear remain fixed in position, driving the 
spindle by sliding keys, as in the ordinary construction. 
The plan generally followed by this company with all its 



FORMING THE TEETH OF SPUR GEARS. 35 

machinery, of building the various parts of the mechanism 
on the unit system and assembling them as units in the 
machines, gives an air of neatness in design to the tool 
which will be readily appreciated from the engraving. A 
feature common with most automatic gear cutters, the 




Fig. 23. Automatic Gear-Cutting Machine made by Cincinnati 
Gear Cutting Machine Company. 



outboard support for the work arbor, will be noticed 
clamped to guiding surfaces on the front of the bed. The 
index wheel is solid, and is made an accurate copy of a 
precision master wheel, as previously explained. 



36 



GEAR-CUTTING MACHINERY. 



The machine in Fig. 23 is built by the Cincinnati Gear 
Cutting Machine Company, of Cincinnati, Ohio. Its most 
noticeable characteristic is the simplicity and directness of 
its mechanism, which is worthy of study as an example of 
good design in this respect. The movements are inter- 
locked to prevent any possible variation from the proper 




Fig. 24. A Machine made by the Newark Gear Cutting Machine Co., 
with Special Shortened Column, for cutting Coarse Pitch Pinions. 

cycle of automatic operation, and a number of distinctive 
conveniences in setting and operation are provided. The 
illustration shows very plainly the weight and stiffness of 
the main castings. 

The spur gear cutter shown in Fig. 24 is built by the 
Newark Gear Cutting Machine Company, of Newark, N. J. 
The machine shown was designed primarily for cutting 



FORMING THE TEETH OF SPUR GEARS 37 

pinions of large pitch. For this reason the machine is 
ruggedly built and has a comparatively short column, 
limiting the diameter range for which it is adapted. The 
whole mechanism is driven from a pulley running at con- 
stant speed, the various changes of spindle speed and feed 
being obtained by change gears. It is like most other 
machines of its class, also, in the fact that the interior of 
the base of the machine serves as a collecting chamber for 
chips and a reservoir for the oil which is drawn from 
them. From here it is returned to the cutter by an oil 
pump. It will be seen that the cutter spindle driving gear 
in this case is a spur gear. The change gearing for alter- 
ing the speed is placed next to it in the order of trans- 
mission, so that the splined shaft which leads the motion 
to the cutter shaft runs constantly at high velocity, what- 
ever the speed of the cutter may be. Smaller machines of 
somewhat similar type are also built by this firm, some of 
them adjustable for cutting bevel gears as well as spur 
gears. This machine may also be supplied with a higher 
column than is here shown, providing for work of greater 
diameter. 

An automatic gear cutter built by the E. J. Flather 
Manufacturing Company is shown in Fig. 25. One of the 
most noticeable features of this machine as compared 
with those previously considered is the construction of the 
column which supports the work-carrying head. This is 
made double, and the work-carrying head passes through 
it instead of being clamped to ways on its face. The 
handle shown projecting at an angle in front of the index 
wheel casing at the back of the column is used for clamp- 
ing the work head solidly to its seat on both the front and 
back sides of the column, when the adjustment for depth 
of cut has been made. The spindle of this machine is 
worm-driven. The indexing mechanism is of the posi- 



38 



GEAR-CUTTING MACHINERY. 



tively operated type, with a friction device to prevent 
rebound. As in previous cases, all changes of feed and 
speed are made by change gears, the machine being driven 
by a constant speed pulley. 




Fig. 25. The Flather Automatic Gear Cutter. 

Another well-known tool in this field is that shown in 
Fig. 26. It is built by Gould & Eberhardt, Newark, N. J. 
In this machine, as in the previous one, the column is 
double and the work-carrying head passes through it. 
This machine is of larger capacity than any of the other's 
shown so far and, in common with most large capacity 



FORMING THE TEETH OF SPUR GEARS. 



39 



machines, is provided with a mechanism for raising and 
lowering the work spindle head by power. Another point 
of interest in this machine is the automatic clamping 
device with which it is provided, used for firmly holding 




Fig. 26- Gould & Eberhardt Spur Gear Machine, with Special Auto- 
matic Rim-clamping Device. 

the rim of the blank while the cut is in progress. This is 
in addition to the usual positive back stop against which 
the blank rests. This clamp consists of a pair of jaws, 
carried by slides on the adjustable arm shown at the front 
of the machine, and operated by a screw connected with 
the mechanism of the machine in such a way as to hold 



40 



GEAR-CUTTING MACHINERY. 



the work firmly while the cut is in progress, releasing it 
while the indexing takes place, and again clamping it for a 
new cut. It is especially useful for comparatively slender 
work. 

The general features of this line of machines can be best 




Fig. 27. Specialized Design of the Gould & Eberhardt Automatic 
Gear Cutter for Heavy Motor Gears. 



seen by referring to Fig. 27, which shows another member 
of this fine, specially constructed for the severe service of 
cutting steel motor gears. The cutter and feed screw are 
in line with each other, so that a direct central thrust is 
imparted to the slide. The machine is driven through a 
single pulley, from which the movement is transmitted 



FORMING THE TEETH OF SPUR GEARS. 



41 



through gearing and keyed shafts to the different parts of 
the machine. The cutter spindle is driven by worm and 
worm-wheel through change gearing. The index wheel is 
of the spUt rim type with hobbed teeth, the final finishing 




Fig. 28. The Largest Size of the Line built by Ludwig Loewe & Co. 

of which is done with the dividing wheel in position on 
the machine. Means are provided for compensating for 
all wear and lost motion which may take place in this 
mechanism. A slight tension is constantly maintained 
between the stop cam and the worm in the direction of 



42 GEAR-CUTTING MACHINERY. 

rotation, which prevents all danger from back lash and 
rebound. The rigid construction of the outer support of 
the work arbor will be noticed. Its base is mounted on a 
bracket cast on the side of the main frame. In removing 
a finished gear from the machine, it slides back out of the 
way without disturbing the height adjustment of the out- 
board bearing. 

An automatic gear cutter of continental design and 
manufacture is shown in Fig. 28. This tool is built by 
Ludwig Loewe & Co., of Berhn, Germany. Its most 
striking feature, so far as appearance is concerned, is the 
provision made for supporting the outer end of the work 
arbor. Two uprights are used, one at the front and the 
other at the rear of the bed, supporting a bearing for the 
work arbor. This bearing is counterweighted, so as to be 
easily adjustable for vertical position. The uprights can 
be moved back when it is desired to insert the work, by 
operating the hand-wheel shown at the base of the front 
one. The spindle of this machine is driven by a worm- 
gear. It has a large dividing wheel for the range of work 
it is intended for, having a diameter of 57 inches. It is 
made in two parts, by the method which generates each 
wheel anew, rather than making it a copy of a previously 
made master wheel. Eight changes of feed are provided, 
varying from .010 to 0.42 inch per revolution of the cutter. 
This machine is also built in two smaller sizes. The size 
shown will cut gears up to 78 inches in diameter. 

The machine shown in Fig. 29 is built by J. Parkinson & 
Sons, Shipley, England. This machine cuts gears up to 
48 inches in diameter by 10 inches face. The cutter 
spindle is driven by a worm and worm-gear, and has four 
changes of speed obtained by a sliding quick change 
gear arrangement, instead of by the usual removable gears. 
The dividing mechanism is driven by friction, and has a 



FORMING THE TEETH OF SPUR GEARS. 



43 



device which starts and stops it gradually to avoid shock. 
The starting and stopping is done by the interposition 
of a pair of elliptical gears which gradually increase the 
rapidity of the indexing movement when it is started, 
and retard it in the same way as it is being completed. 
By means of suitably arranged connections, provision is 
made for multiple indexing, which is often resorted to, to 




Fig. 29. An Example of English Design, built by J. Parkinson & Son. 



avoid local heating. In cutting a gear having 45 teeth, 
for instance, every fourth tooth may be cut continuously, 
until the gear is completed. In this way the heat due to 
cutting is distributed more uniformly around the rim, 
avoiding the distortion due to local heating, which is liable 
to occur when teeth are cut in regular order. This multii)le 
indexing is obtained without requiring the change gears to 
be specially calculated for it. 



44 



GEAR-CUTTING MACHINERY. 



A gear cutter made by J. E. Reinecker, of Chemnitz- 
Gablenz, Germany, is shown in Fig. 30. The index wheel 
of this machine is of large diameter, about seven-tenths of 
that of the largest gear that can be cut. The mechanism 
controlhng the movements of the machine is so arranged 
that the forward feed does not commence until the indexing 




Fig. 30. The Reinecker Automatic Spur Gear Cutting Machine. 

has been completed, the cutter slide being retained in 
its rearward position until that time, thus avoiding the 
possibility of damage to the machine or work from failure 
of the mechanism to operate properly. An unusual feature, 
seen at the rear of the machine in the illustration, is the 
spindle drive gearing. The spindle is driven by a worm. 
This is not of the ordinary type, with a hole through its 



FORMING THE TEETH OF SPUR GEARS. 



45 



center, splined to be driven by the longitudinal shaft on 
which it slides as the table is fed forward or back; instead, 
a long worm is used, fixed longitudinally, and threaded 
for a sufficient length to accommodate the worm-wheel 




Fig. 31. A German Automatic Spur Gear Cutter which shows the 
Influence of American Design. 



throughout the full travel of the sHde. It will also be 
observed that the outboard support for the work arbor is 
hinged to facilitate the insertion and removal of the work. 
A German machine, very similar to that shown in Fig. 22, 
is illustrated in Fig. 31. The mechanism is carefully 
enclosed, fixed handles are provided for all the adjustments, 



46 



GEAR-CUTTING MACHINERY. 



and standard types of rim rests, outboard work supports, 
etc., are furnished. The speed and feed changes, as well 
as the indexing, are effected by change gears. The machine 
is built by Schubert & Sulzer, Chemnitz, Germany. 

A gear cutter built by Messrs. G. Wilkinson & Son, of 
Keighley, England, is shown in Fig. 32. This is essentially 
the same in principle as the previous machines described, 




Fig. 32. The Wilkinson Automatic Machine for Small Gears. 



but it has an entirely different appearance, due to the fact 
that the bed is set on legs, instead of extending down to a 
sohd bearing on the floor. The controlling mechanism is 
also somewhat differently arranged, although the move- 
ments required are the same. It will be seen that it is 
intended for comparatively small work. It takes wheels 
up to 18 inches in diameter and 6 diametral pitch. The 
cutter spindle is driven by a spur gear of large diameter. 



FORMING THE TEETH OF SPUR GEARS. 



47 



Standard Type of Automatic Formed Cutter 
Machine for Heavy Work. 

The machines we have just been describing are repre- 
sentative of the standard form of automatic machine 
for small and medium work. Considerations of ease 




Fig. 33. A Small Armstrong-Whitworth Automatic Machine. 

of handling the work and convenience in arranging the 
mechanism have evolved a somewhat different form of 
machine for the largest and heaviest work. The change 
made may best be described by saying that the previous 
type of machine is laid down on the back of its column, with 
the bed extending vertically upward into the air. In other 



48 GEAR-CUTTING MACHINERY. 

words, the change is simply a change of base. The bed 
becomes the column, and the column becomes the bed. 
This explanation will be easily understood by comparing 
the machines shown in Figs. 35 to 38 with those in Figs. 22 
to 31. The principal advantage due to the change of base 
in this machine is the better support given to heavy work, 
the weight of which is carried directly by the bearing of 
the slide on the bed, instead of being taken by the elevating 
screw in the column, as in the design previously described. 

Although it was stated that this construction was espe- 
cially adapted for heavy work, the first three machines of 
this type here illustrated are comparatively small. That 
shown in Fig. 30 is built by Sir W. G. Armstrong, Whitworth 
& Co., Manchester, England. The machine is very simple in 
design and ruggedly built. The slow downward feed and 
quick return are obtained by epicyclic gearing in the feed 
cone at the top of the column. The clutches controlling 
this mechanism are operated by adjustable dogs on the 
side of the column. The indexing mechanism is of the 
frictional type, set by change gears for the required number 
of cuts. 

The gear-cutting machine shown in Fig. 34 is built by 
John Hetherington & Sons, Ltd., of Manchester, Eng- 
land. A number of interesting points are evident from 
the cut. For instance, as may be seen, the vertical feed 
of the cutter slide on the face of the column is effected by 
a cam under the base, at the end of the horizontal bearing 
in the rear leg. This cam, and the roller and slide which 
it operates, are plainly visible beneath the machine. The 
slide is counterweighted to keep the roll always pressed up 
against the cam. Another ingenious detail of the mech- 
anism is he belt tightener provided, which compensates 
for the change in position of the cutter slide. The belt 
is passed over an idler fastened to one end of a bell crank, 



FORMING THE TEETH OF SPUR GEARS. 



49 



whose other arm has teeth engaging a rack on the cutter 
sHde. As the sUde descends, requiring more belt, the 
idler moves toward the right, furnishing the required 
amount. The same belt drives both the spindle mechan- 
ism and the feed mechanism. The index worm and 




Fig. 34. A Simple Machine with Cam-operated Feed, built by John 

Hetherington & Sons. 



wheel are beneath the table. A quick withdrawing motion 
operated by an eccentric lever is provided for bringing the 
spindle back from the cutter when it is desired to remove 
or replace work on the arbor; this can be operated without 
disturbing the setting for depth of cut. This machine 
will cut gears up to 30 inches in diameter, 4 inches face 
and 4 diametral pitch. The proper change gears for 
varying the feed and indexing are furnished with the 
machine. 



50 



GEAR-CUTTING MACHIxNERY. 



The first of the heavier machines here shown, in Fig. 35, is 
another built by Sir W. G. Armstrong, Whitworth & Co. 
of Manchester, England. In this machine the index 
wheel is carried above the bed, while a second bearing for 
the work spindle is provided by the arm which springs 
from the work shde on either side and spans the index 




Fig. 35. Heavy Armstrong- Whitworth Gear-Cutting Machine. 

wheel. This brings the top of the base rather low, so the 
column is carried on an upward extension of the bed, 
giving the whole structure a distinctive appearance. The 
change gears for indexing are mounted on the shde, and 
carried with it when adjustment is made for diameter. 
In this machine the indexing is either automatic or hand, 
as may be thought best. There is less gain in automatic 
indexing in very heavy work than in the medium size, since 
the time of feeding is proportionately longer, while the 
large machine should have at least as much attention as 



FORMING THE TEETH OF SPUR GEARS. 



51 



. ■ ^ ■ r. Tho putter head of this machine 

^^ Tl^U :r ™if cS:e:Ct;.ash,„g wonu-wheds. 
can be set on an an^ie bearing 

ThecutterspindleisBupportedatlu^o U--^^ Y .^ 

onrl k driven bv a coarse lead worm ^cai. xi^ 
iLf r t Jeuttn.g of wheels fro.n 12 to 96 inches in 
diameter, up to 14 inches face. 




F.0 36 AnExampleofSwedishDesign-TheAtlasMachincas 
arranged for cutting Spur Gears. 

The machine shown in Fig. 36, built by Nya Aktiebokget 
Mas, Stockholm, Swede, ^--^n ^^^^^^^ a stac.^^oj 

Sr\"nT-adaptrtrmiing spiral and worm 
Ta; as well as spur gears, so that it has mechanism m 
^Z to that needed for cutting spur goars on y a 
H,ay be seen from the illustration. The heavy cross 



52 



GEAR-CUTTING MACHINERY. 



and the change gearing mounted on it are part of the 
mechanism required for cutting worm-wheels. Its action 
as a spur gear machine is automatic and similar to that 
of the machines previously described. Like the Arm- 



f^-^ 




Fig. 37. The Darling & Sellers 4-foot Automatic Spur Gear 
Cutting Machine. 

strong gear cutter in Fig. 35, it has the index wheel above 
the bed. The machine will cut gears up to about 8 feet 
in diameter. Other apphcations of this tool are illus- 
trated later in Figs. 77, 104 and 146. 

The machine shown in Fig. 37, built by Darling & 



FORMING THE TEETH OF SPUR GEARS. 53 

Sellers, Keighlcy, England, has the index wheel carried 
below the bed with the work spindle passing up through it. 
It will also be noted that the work carriage encircles the 
bed, having bearings on its sides, as well as being gibbed 
at top and bottom. The cutter spindle is driven by helical 
gearing. The spindle is hardened and carried in a long 
taper bearing, which is carefully ground to fit. The end- 
wise adjustment for centering the cutter is effected by 
moving the main spindle bearing bodily to the left or 
right. A permanent gauge is attached to the cutter slide 
which can be instantly lowered to test the centering of the 
cutter. A novel feature of this gear-cutting machine is 
the way in which the quick return of the cutter slide is 
effected by the excess weight of the counterbalance, which 
brings the slide immediately to its upper position when the 
feed is released, stopping against an air cushion. The 
feed change is accomplished by change gearing. The 
indexing device is of the friction type, but so interlocked 
with the feeding mechanism as to prevent the feeding 
of the cutter before the indexing has been completed. A 
larger size of this machine is provided with a clamping 
arrangement which firmly holds the rim of the work while 
the cut is being taken. This works automatically; a 
friction drive acting through a screw presses it down onto 
the work, while a positive clutch raises it again. The 
machine shown in the cut has a feed of 16 inches and will 
swing a 4-foot gear. The whole design of the machine 
is unusually interesting and attractive. 

In Fig. 38 is shown an automatic gear-cutting machine 
built by the Newton Machine Tool Works, Philadelphia, JPa. 
This is intended especially for the cutting of heavy gears 
made of high carbon steel, such as are used in motor gears 
for electric cars, locomotives, etc., with the expectation of 
cutting two or three teeth at once. The massive propor- 



54 



GEAR-GUTTING MACHINERY. 



tions of the machine give evidence of the duty for which 
it is intended. It is provided with a mechanism which 
renders it impossible to engage the downward feed until 
the dividing has been successfully completed for the next 




Fig. 38. A Newton Machine, especially designed for the cutting of 
Heavy Motor Gears and Pinions. 

tooth. The machine shown is directly motor-driven, the 
spindle being connected to the motor through a train of 
spur, spiral, and worm gearing. The indexing worm- 
wheel is mounted above the sUde, as may be seen. 



FORMING THE TEETH OF SPUR GEARS. 



55 



Machines for Heavy Work with Column 
Adjustable for Diameter. 

A modification of the heavy type of machine consists 
in making the column carrying the cutter shde adjustable 
on the bed to suit the diameter of the work, instead of 
adjusting the work spindle. An automatic machine of 





Fig. 39. The Craven Automatic Gear-Cuttino; Machine. 



this type is shown in Fig. 39. This tool is built by Craven 
Brothers, Ltd., Manchester, England. The spindle head 
is counterbalanced, and is provided with four feeds which 
may be changed by a quick acting mechanism at the front 
of the machine. The cutter spindle is driven by a steep 
pitch worm and gun-metal worm-wheel. The outer end 
is supported in an adjustable bearing. The dividing 
mechanism can be operated either by hand or power. 



56 



GEAR-CUTTING MACHINERY. 



The design is a neat one and shows evidence of careful 
planning. 

Tlie adjustable column machine shown in Fig. 40 is 
built by Gould & Eberhardt, of Newark, N. J. This is 
the 15-foot size of a line of three, of which the largest will 
cut, entirely automatically, gears up to 20 feet in diameter, 
36 inches face and 6 inches circular pitch in cast iron, or 




Fig. 40. The Horizontal Type of Gear Cutter, as built by Gould & 

Eberhardt. 



4i inches in steel. So far as the writer knows, this latter 
machine is the largest entirely automatic spur gear cutting 
machine that has ever been built. There are a number 
of interesting features in the design and construction of 
this machine. A safety device is incorporated in the 
indexing mechanism which makes it impossible for the 
cutter to feed downward before the indexing has been 
successfully completed. An auxihary cutter spindle (shown 



FORMING THE TEETH OF SPUR GEARS. 



57 



in place in the machine) is provided for finer pitch, 
small diameter cutters. When the heaviest work is being 
done, this small spindle and the boxes which support it 
are removed. The column has rapid power adjustment 




Fig. 41. The Hetherington Automatic Gear-Cutting Machine. 

on the bed with fine hand adjustment for the final setting. 
This line of machines has been largely used in cutting cast- 
iron and steel gears which had formerly been made with cast 
teeth, giving very much better gears at an expense not 
much greater than was required for those with cast teeth. 



S8 GEAR-CUTTING MACHINERY. 

In Fig. 41 is shown a machine of the adjustable col- 
umn type built by John Hetherington & Sons, Ltd., of 
Manchester, England. This is a large capacity machine, 
being fitted for cutting gears up to 8 feet in diameter' 
16 inches face and 1 diametral pitch. The dividing 
mechanism may be operated either automatically or by 
hand. In the former case the indexing is effected by 
means of a ratchet mechanism operated by a crank which 
starts the movement gradually and stops it in the same 
way, without shock and without danger of over-running. 
The spindle is driven by worm and spur gears from a 
3-step cone pulley, driven by a wide belt running at high 
velocity. The worm-gear is of gun metal, and the worm 
of steel. 

Spur Gear Cutting Machines with L-shaped Bed. 

As the machines we have been describing for heavy 
work were evolved from the orthodox gear cutter by the 
expedient of laying that machine on its back and trans- 
forming the base into the column and vice versa, so a third 
type, occasionally met with, has resulted from laying the 
orthodox machine on its side, producing a bed having an 
L-shape. The old Pratt & Whitney gear-cutting machine 
was an example of this. This is famiUar to most mechanics 
engaged in gear cutting, as there are many of them in use 
in various shops in this country for cutting spur gears and 
bobbing worm-wheels. The builders have discontinued 
making the machine, however, so we do not show it here. 

Fig. 42 shows a contemporaneous example of this type, 
built by G. F. Smith, Ltd., of Halifax, England. As may 
be seen, one branch of the L furnishes ways on which the 
horizontal work spindle is adjusted to set the machine for 
the proper diameter of work. The other portion of the 
bed furnishes ways for the slide carrying the vertical cutter 



FORMING THE TEETH OF SPUR GEARS. 59 

spindle. This spindle is driven by spiral and worm 
gearing from a cone pulley. The indexing worm on the 
dividing wheel shaft is adjustable in the center to take up 
wear. All changes of feed and indexing are by positive 
gearing. An outboard support for the work spindle is 




Fig. 42. An Example of Machine with L-shaped Bed, as made by 

G. F. Smith, Ltd. 

plainly shown in the cut attached to the outer end of the 
cutter-slide branch of the bed. 

Another example of this type of machine, though 
arranged with adjustments permitting the cutting of bevel 
gears, is that built by the Newark Gear Cutting Machine 
Company, shown in Fig. 172. 

Precision Formed Cutter Machines. 

The machines we have described are suited for the 
cutting of gears ranging from those used in machinery of 
ordinary size up to the largest and heaviest built. Tliere 



GO GEAR-CUTTING MACHINERY. 

has been a development along somewhat different lines 
in machines for cutting teeth in minute pinions and gear 
blanks, such as are used in watches, fine instruments, etc. 
Some of these small machines cost as much as, or more 
than, larger ones for ordinary work. This is due in part 
perhaps to their complexity, but more to the accurate 
fitting necessary. An amount of play which would be 
just sufficient to provide oil space in the spindle of a large 
automatic gear-cutting machine, would give so loose a fit 
to the spindle of one of these minute mechanisms as to make 
it totally unfit for the work it has to do. AVhere the thick- 
ness of the teeth of the gear being cut is a matter of a few 
thousandths only, the required accuracy in the fitting of 
the spindle, slides, etc., must be expressed in tens of 
thousandths or even hundreds of thousandths of an inch. 
Even though a high degree of accuracy in fitting is ob- 
tained in these machines, it is often found necessary to 
take two or three and sometimes more cuts through each 
tooth space in order to make sure that the desired outline 
is obtained. In one of the machines here described provi- 
sion is made for this automatically. 

In Fig. 43 is shown a precision gear-cutting machine 
built by Hardinge Brothers, 1036 Lincoln Avenue, Chicago, 
111. It will be seen to follow somewhat in its mechanism 
the Slate and Sloan & Chace machines, shown in Figs. 19 
and 20, being derived in form from the ordinary column 
and knee type of milling machine, though greatly reduced 
in size. In adjusting for diameter, however, the cutter 
spindle is moved up or down by swinging about the fulcrum 
of the arm on which it is carried ; the table or slide carrying 
the w^ork head-stock and foot-stock is not adjustable 
vertically for this purpose. The feeding and indexing 
movements are efi"ected by a cam shaft driven by the 
large wheel shown at the back of the machine. The feeding 



FORMING THE TEETH OF SPUR GEARS. 61 

is governed by the slotted link mechanism at the front, 
connected by the adjustable reach rod shown with the 
bracket extending downward from the work table beneath 
the dividing head. Index plates are used instead of the 
index worm-wheel common in larger machines. Separate 
disks are used for locating the spindle and locking it in 
position after the indexing, the disk for the latter purpose 




Fig. 43. The Harclinge Automatic Precision Gear Cutter. 

being covered to prevent accidental injury. An arrange- 
ment is provided by which the cutter is lowered from the 
cut on the backward movement to prevent injuring the 
finished tooth space, and to allow the indexing to take 
place during the return movement. The ratchet wheel 
shown below the machine at the right is indexed a step for 
each tooth cut in the work, and may be set to lower the 
cutter out of the work and stop the feeding mechanism 
when all the teeth have been cut. The cutter spindle 



62 GEAR-CUTTING MACHINERY. 

still runs, however, and the indexing still proceeds, so that 
the working parts are constantly kept at the working tem- 
perature. 

In Fig. 44 is shown a precision gear cutter made by the 
Standard Manufacturing Company, of Bridgeport, Conn. 
This machine has the indexing and feeding mechanisms 
operated by a cam shaft driven by the worm and worm- 
wheel shown at the left of the machine. It will cut gears 
up to 4 inches in diameter, in stacks 2 inches long. As in 




Fig. 44. The Standard Manufacturing Company's Automatic Pre- 
cision Gear Cutter. 

the previous machine, the cutter is raised out of the work 
while the blank is being indexed and the feed is being 
returned to commence the next stroke. Two speeds are 
provided for the cutter spindle, and nine feeds. The 
cutter works ninety per cent of the time, the indexing and 
returning movements being very rapid. Both the work 
and cutter spindles have tapered bearings adjustable for 
wear. 

The machine shown in Fig. 45, made by the Sloan & 
Chace Manufacturing Company, Newark, N. J., is built 
on the same general plan as the previous machines so far 



FORMING THE TEETH OF SPUR GEARS. 



63 



as concerns the use of dial plates for indexing and cams 
for performing the various movements. This machine, 
however, can be arranged to carry three cutters on the 
spindle if desired. The first cutter is used for roughing, 
the work being indexed clear around for that purpose. 
The cutter spindle is then shifted axially to bring the second 
cutter central with the w^ork, when the operation is con- 
tinued as before. The spindle is then shifted a second 




Fig. 45. The Sloan & Chace Automatic Precision Pinion Cutter, 
arranged for taking Three Cuts through Each Tooth. 



time to bring the third or finishing cutter into position for 
operation, whereupon the work is completed. This little 
machine is ingeniously arranged to allow all three of the 
settings (the roughing, secondary, and finishing) to be 
separately adjusted for centering the cutter and depth 
of cut. All the movements are entirely automatic. The 
machine is essentially a pinion cutter rather than a gear cut- 
ter, as it is best adapted for gears having comparatively few 
teeth. 
The automatic pinion-cutter shown in Fig. 46 is made by 



64 



GEAR-CUTTING MACHINERY. 



the Waltham Machine Works, of Waltham, Mass. In this 
machine the automatic principle has been developed to a 
high degree, in that the machine feeds itself and takes 
out the work as well after it is completed. The long slide 
seen extending upward from in front of the cutter is a 
magazine in which pinion blanks are placed. This magazine 
is brought in line with spindles of the head and foot stock, 
which (by the action of the cams by which they are 




Fig. 46. The Waltham Automatic Pinion Cutter, with Magazine and 

Self-feedino; Mechanism. 



controlled) grasp the shanks of the blank and hold it 
firmly in position to be cut. The cutting and indexing 
then proceed as in previous machines. When the indexing 
has been completed, the hold of the chucks on the work is 
released and the work ejected. This operation is contin- 
uous as long as the cutter stays sharp and the magazine 
is kept full. 



FORMING THE TEETH OF SPUR GEARS. 



Q6 



The Formed Tool Principle applied to the Grinding 
OR Abrasion Process. 

The only representative of this process, so far as we 
know, is the machine shown in Fig. 47. This tool, built 
by Upton & Gilinan, Lowell, Mass., is intended primarily 
for smoothing up teeth of cast gears, so perhaps it does 
not really belong in the category of gear-cutting machines ; 




Fig. 47. The Upton & Gilman Machine for Finishing the Teeth of 
Cast Gears by Grinding with a Formed Wheel. 



as the only representative of its class, however, it has been 
included. The grinding wheel is formed to the shape of the 
tooth space of the gear to be finished. The gear is mounted 
on the vertical spmdle shown. When the machine is in 
operation the emery wheel is brought down through the 
tooth space, cleaning it out, and is then withdrawn. The 
work is indexed, and the operation is repeated. Owing 
to the fact that the shape of the space and the shape of 
the wheel are the same, the latter tends to preserve its 



66 GEAR-CUTTING MACHINERY. 

form, being used merely to remove irregularities in other- 
wise correctly shaped surfaces. 

Besides the machines thus far described, a number of 
those primarily designed for cutting hehcal and bevel 
gears are adapted to the cutting of spur gears by the form 
tool method as well. Examples of such machines are 
shown in Figs. 110 and 167 to 172 inclusive. 

The Templet Principle applied to Cutting the Teeth 

OF Spur Gears. 

The templet principle is practically limited, in the cut- 
ting of spur gears at least, to the shaping or planing pro- 
cess. Of these machines two examples are here shown. 

Fig. 48 illustrates a templet spur gear planing machine 
built by the Gleason Works, Rochester, N. Y. In this 
tool the work spindle is horizontal, a pit being provided 
for gears of large diameter. The capacity of the machine 
is very great, it being adapted to cutting teeth in blanks up 
to 20 feet in diameter. The cutting tool is, mounted in 
a travehng head at the right side of the machine. This 
traveling head is driven by a screw controlled by open and 
crossed belts and shifting mechanism similar to that used 
for a planer. The scale of the engraving is too small to 
show the templet mechanism clearly, but it is identical in 
principle with that illustrated in Fig. 2, in the first 
chapter of this book. For varying the diameter adjust- 
ment to suit the blank being operated on, the head-stock 
carrying the work spindle is moved toward or away from 
the tool sHde. The machine shown is motor-driven. 

Another remarkable example of templet machine for 
spur gears is shown in Fig. 49. In this case the tool is 
a modified slotter instead of being a modified Richards 
planer as in Fig. 48. The column part of this tool is, in 
fact, practically the portable slotter built by its makers, 



FORMING THE TEETH OF SPUR GEARS. 



67 



the Newton Machine Tool Works, Philadelphia, Pa. It is 
mounted on a long base plate, and may be set at any 
desired position thereon to agree with the diameter of the 
gear being cut. The work is supported on a rotating 
table which is indexed by a worm and worm-wheel oper- 
ated through change gears by a separate electric motor 
provided for that purpose. The head may be moved 




Fig. 48. The Gleason Templet Spur Gear Planer. 



back far enough to swing work 40 feet in diameter. The 
templets for shaping the tooth outline are mounted in 
brackets on the tool head on either side of the tool-post 
of the portable shaper. The tool-post is pressed toward the 
right or left hand former by a spring, as may be required, 
and as it is fed outward by the feeding mechanism provided, 
it is thus shifted sidewise in such a fashion as to reproduce 
the outhne of the templet on the teeth of the gear. 



68 



GEAR-CUTTING MACHINERY. 



It has been used principally for large gears having teeth 
of very coarse pitch, too large to be formed by a formed 
tool or cutter covering the whole outhne. It has the 
advantage over the formed cutter process of being com- 




FiG. 49. The Newton Portable Slotter, arranged with Templet Mechan- 
ism and Indexing Base for cutting Spur Gears. 

paratively simple in operation and adapted to special 
work at a minimum of expense, it being considerably 
cheaper to make a templet than to make a formed and 
reUeved cutter of the same size. 



CHAPTER III. 

MACHINES FOR FORMING THE TEETH OF SPUR GEARS. 

{Continued.) 

With the molding-generating principle the operations 
which have been found most practical are planing or 
shaping, milling, and, to a very limited extent, grinding 
or abrasion. For spur gears, so far as the writer knows, no 
use has been made of the operation of impression ; it would 
be as practicable as in the case of bevel gears, of which an 
example will be shown later (Figs. 194 and 195), but 
there is no need for trying it. In the shaping process the 
commercial use of the molding-generating idea is confined 
largely to one machine, which has found a very extended 
a})plication. In the miUing process there has been a won- 
derful development in the past few years, which is wit- 
nessed to by the large nimiber of machines we are able to 
show involving this operation. But one example of the 
use of grinding can be illustrated. 

Molding-Generating Machines Working by Shaper 

Action. 

In Fig. 50 is shown an automatic spur gear cutting 
machine made by Hugo Bilgram, Philadelphia, Pa., and in 
use in his plant. The tool acts as a rack tooth, and gen- 
erates the gear teeth in accordance with the principle of 
Fig. 8. Instead, however, of finishing one tooth space 
complete and then indexing to the next one, the operation 
is continuous. As has been explained, in th(> mokling })ro- 
cess the blank and tool must b(^ rolled on each other as 

09 



70 



GEAR-CUTTING MACHINERY. 



if the former were a gear meshing with a rack, of which 
the latter represents a tooth. In the Bilgram machine, 




Fig. 50. The Bilgram Automatic Spur Gear Generating Machine, using 
a Shaper Tool shaped like a Rack Tooth. 

instead of having this rolHng action take place for each 
tooth, it takes place but once in the completion of the 
gear. The tool starts in at one side of the blank, being 



FORMING THE TEETH OF SPUR GEARS. 



71 



given a motion similar to that given by a shaper. It cuts 
its first stroke in the work, wliich is thereupon indexed for 
the tool to take a second cut in the next tooth. This 
indexing proceeds with every stroke of the shaper ram, so 
that the teeth are all formed together. Besides the rota- 
tion of the blank due to the indexing, there is imposed on 




Fig. 51. Elevation of a French Spur Gear Generating Machine 
employing a Rack Tooth Form of Shaper Tool. 

this that which we have described as being necessary for 
the rolHng motion. For this, the blank is uniformly 
rotated, and the ram carrying the tool is fed along side- 
ways to agree with the motion of the imaginary rack. 
These various movements are all attended to by change 
gearing. It will be seen that with this machine, as with 
others of the molding-generating type, but a single tool 



72 



GEAR-CUTTING MACHINERY. 



is needed for a given pitch. This may be used to cut any 
gear, from the smallest to the largest. 

The machine shown in Figs. 51 and 52, operating on 
the same principle, is built by the Societe Frangaise de 
Machines-Outils, St. Ouen, Paris. The resemblance of this 
machine to a slotter is at once evident. The work, which 




Fig. 52. Face View of French Spur Gear Generating Machine. 



is shown mounted on the work arbor at C, is carried by 
table B, which is adjusted in and out on the bed A of the 
machine for diameter. The tools G, having the outline of 
the rack tooth, are mounted on a ram D, which is, in turn, 
guided in a cross slide E, which travels on a cross rail 
solid with the frame of the machine. In cutting a tooth 
the tool starts in at one side of the blank, and the ram D 



FORMING THE TEETH OF SPUR GEARS. 73 

on cross slide E is fed from right to left, in the face view 
of the machine. This lateral motion is transmitted by 
means of rack teeth on arm F, engaging suitable mechan- 
ism on the work table for rotating work C in unison with 
the lateral movement of the tool. When one tooth has 
thus been cut, and the slide E has been returned to the 




Fig. 53. An English Spur Gear Generating Machine employing 
Multiple Tools of Rack-shaped Outline. 

starting point, the work is indexed, and a second cut is 
taken in the same manner — and so on until all the teeth 
are cut. The capacity of this machine is for work up to 
20 inches in diameter. 

A third machine is built by Spencer & Spiers of Hud- 
dersfield, England. The construction and movements are 
entirely different from the previous examples, though the 



74 



GEAR-CUTTING MACHINERY. 



principle is the same. There are two sets of tools AA, as 
shown in the plan view Fig. 54, disposed on opposite sides 





Fig. 54. Plan and Vertical Section through the Machine shown in 
Fig. 53, with Details of Controlling Mechanism. 

of the work B. Each of these tools is formed of several 
rack teeth. As the work is reciprocated up and down 



FORMING THE TEETH OF SPUR GEARS. 75 

between them by crank G and connecting-rod F , these 
tools are fed oppositely in the direction of their pitch lines, 
and the work is revolved in unison at the proper ratio. 
To effect this the tools are mounted on parallel sUdes E, 
which carry racks engaging gear D, within the base of the 
machine. D also has worm-wheel teeth cut on it, driven 
by a worm which is connected by change gearing with 
worm-wheel C, which rotates the work. Owing to the 
fact that the two tools have several teeth each it is pos- 
sible to finish pinions and small gears at one passage. 
For larger gears, provision is made for bringing the tools to 
the starting point again, and taking a second cut, with the 
work turned to present a new portion of the periphery to 
the action of the cutting edges. 

The makers of this machine state that no outboard 
supporting bearing for the work arbor has been found 
necessary, owing to the fact that the cuts are perfectly 
balanced. This is effected by the use of the two tools, 
one on each side of the work. A larger machine has been 
built in which the tool slides reciprocate vertically instead 
of the work, the latter being mounted on a spindle which 
revolves as the cutters are fed past it. The design illus- 
trated in Figs. 53 and 54 has been somewhat improved in 
later models. 

The other machine we show of the molding-generating 
type involving the shaping process is one widely used, 
built by the Fellows Gear Shaper Company, of Spring- 
field, Vt. One of these machines is shown later in Fig. 79, 
engaged in cutting an internal gear, while in Fig. b^ is a 
nearer view which shows the action of the cutter in form- 
ing the teeth of a long spur pinion. The principle by 
which it operates is exactly that shown in Fig. G. The 
cutter is a gear having the outline of a member of the 
interchangeable series to which the gear to be cut belongs. 



76 



GEAR-CUTTING MACHINERY. 



It and the blank are rotated together in the proper ratio. 
The cutter is first fed in to full depth and then the rota- 
tion is started and continued until the full periphery of 
the work has been formed. It is understood, of course, 
that the cutter is given a vertical shaping movement by 
the ram to which it is attached. The proper ratio between 
the cutter and the blank is obtained by change gears set 




Fig. 55. Detailed View of the Fellows Gear Shaper in Action; 
see also Figs. 79 and 94. 



for the number of teeth it is desired to have in the gear. 
The movements of the machine are automatic, in that 
when it has been set for the pitch of cutter and number 
of teeth, the machine will automatically feed itself to 
depth, stop this feeding and commence the slow rotary 
movement, continuing this until the work is completed, 
when the machine will stop. In the case of gears which 
have to be very accurately cut in refractory materials, 
provision is made for automatically taking a second cut 



FORMING THE TEETH OF SPUR GEARS. 77 

around at a slightly increased depth, so as to give assur- 
ance that the form of the tooth is as true as can be 
obtaincnl. There are many interesting phenomena con- 
nected with this method of gear cutting which cannot be 
entered into here. 

The Molding-Generating Milling or Hobbing Machine 

AND ITS Action. 

The most widely used process involving the milling oper- 
ation of molding-generating is the hobbing process. The 
principle of this method is shown diagrammatically in 
Fig. 5(3. Here we have an imaginary rack meshing with 
a gear, and molding its teeth in the same way as in Figs. 7 
to 10. The teeth of this rack, shown in dotted outline, 
coincide with the outlines of a hob, shown in full lines, 
which has been set at such an angle as to make the teeth 
on its front side parallel with the axis of the gear. In 
other words, it has been set at the angle of its helix, meas- 
ured at the i)itch line. It will be seen that the teeth of 
the hob, when set in this position, correspond with the 
teeth of the rack. If, now, the hob and blank be rotated 
at the ratio required by the number of threads in the hob 
and the number of teeth in the gear, this movement will 
cause the teeth of the hob to travel lengthwise in exactly 
the same way as the teeth of the imaginary rack would 
travel if in mesh with the gear whose teeth are to be cut. 
It will thus be seen that the hob fulfills the recjuirements 
necessary for molding the teeth of the gear to the proper 
form. In practice the hob is rotated in the required ratio 
with the work, and fed gradually through it from one 
side of the face to the other. When it has passed through 
once, the work is completed. 

Of the great number of machines built during the past 
few years involving this principle, many are arranged for 



78 



GEAR-CUTTING MACHINERY. 



cutting spiral gears as well as spur gears. In describing 
these tools part of them have been classed as spur gear 
cutting machines, while the remainder will be found 
under machinery for cutting spiral gears. (See Figs. 117 
to 128 inclusive.) Of course, all of the machines in the 




GEAR BEING CUT 

(HELIX ANGLE 
OF HOB AT 
PITCH SURFACE 

WORM REPRESENTING THE 
HOB WHICH IS CUTTING THE 
GEAR 




IMAGINARY RACK WHICH 
FORMS THE GEAR BY THE 
MOLDING GENERATING PRO- 
CESS-ITS TEETH COINCIDE 
WITH THOSE OF THE HOB 
WHEN THE LATTER IS 
SET AS SHOWN 



GEAR BEING CUT 



Fig. 56. Diagram illustrating the Principle of the Hobbing-Process 

of Forming Spur Gears. 



latter division are capable of cutting spur gears also, and 
in referring to machines for cutting spur gears they should 
be classed with those described in the following para- 
graphs. Some of the machines illustrated in Figs. 58 to 72 
can be used for cutting spiral gears as well, but have been 
described in this chapter because the engravings we have 
at our disposal show them arranged for cutting spur gears. 



FORMING THE TEETH OF SPUR GEARS. 79 

The spiral gear hobbing machine bears about the same 
relation to the plain spur gear hobbing machine that the 
universal miller does to the plain milling machine. The 
added adjustments and mechanism required in each case 
tend to somewhat limit the capacity of the machine in tak- 
ing heavy cuts, though they add to its usefulness by extend- 
ing the range of work it is capable of performing. The 
requirements of the successful gear hobbing machine are : 

First. A frame and mechanism of great rigidity. 

Second. Durable and powerful driving mechanism. 

Third. Accurate indexing mechanism. 

The first requirement is one of great importance, not 
only in its influence on the heaviness of the cut to be 
taken and the consequent output of work, but on the 
matter of accuracy as well. The connection between the 
hob and the work, through the shafts and gearing, is 
liable to be so complicated that the irregular cutting 
action of the hob produces torsional deflections in the 
connecting parts, leading to serious displacement from the 
desired relation between the hob and the teeth being cut. 
This displacement from the desired position results in 
teeth of inaccurate shape, weak and noisy at high speeds. 

In its effect on the output, rigidity is even more impor- 
tant in the hobbing machine than in the orthodox auto- 
matic gear cutter. A heavier cut is taken, since a greater 
number of teeth are cutting on the work at once. The 
number of joints between the cutter and the work-sup- 
porting table and spindle must therefore be reduced to 
a minimum, and the matter of overhang both for the work 
and the cutter must be carefully looked out for. The 
reduction of overhang is hampered at the cutter head by 
the necessity for a strong drive and an angular adjust- 
ment. In the case of the work-supporting parts it is 
difficult to bring the cutting point close to the bearing on 



80 GEAR-CUTTING MACHINERY. 

account of the necessity for plenty of clearance below the 
work for the hob and its driving gear to run out into. 

The matter of design of the driving mechanism for the 
hob and the work is a difficult one. Not only must it be 
rigid for the sake of accuracy, as previously explained, 
but careful attention must be given to durability as well. 
It requires great skill to design a durable mechanism for the 
purpose within the limitations imposed — in the cutter head 
by the necessity for reducing the overhang, and in the work 
table by the high speed required for cutting small gears. 

Since the indexing wheel works constantly and under 
considerable load, it and the worm must be built of such 
materials as will preserve their accuracy after long con- 
tinued use. Particular attention should be given to the 
homogeneity of the material of the index worm-wheel, to 
make sure that it does not wear faster on one side than 
on the other. 

The field of the hobbing process for cutting spur gears 
has not yet been definitely determined. In some work it 
appears to have certain advantages over the usual type of 
automatic gear-cutting machine, while in other cases it 
falls behind. It will doubtless require continued use, with 
a variety of work, and for a considerable length of time, to 
determine just what cases are best suited for the hobbing 
machine, and what for the machine with the rotating disk 
cutter. It is not probable that in the future either of 
them will occupy the field to the exclusion of the other. 

A Milling Machine Attachment for Hobbing 

Spur Gears. 

It is evident that the universal miUing machine can be 
used for hobbing if suitable connections are made between 
the work and the cutter spindles. The miller shown in 
Fig. 57 is fitted with such connections, through an attach- 



FORMING THE TEETH OF SPUR GEARS. 



81 



ment made by the R. K. LcBlond Machine Tool Company, 
Cincinnati, Ohio. The work is mounted between index 
centers whose index worm-wheel is connected with the 
cutter arbor by a series of gears and splined shafts which 




Fig. 57. Hobbing a Spur Gear with the Hobbing Attachment on a 
Universal MiUing Machine. 

permit free adjustment of the table in any direction. 
The table is set at the angle of the hob, and the action 
obtained is identical with that in Fig. 5G. 



A Column and Knee Type Spur Gear Hobbing 

Machine. 

The first gear hobbing machine we show (see Fig. 58) is 
built by J. E. Reinedver of Chemnitz-Gablenz, Germany. 
This builder was one of the first to make a commercial 
success of the hobbing process, having applied it several 
years ago in his '^Universal" gear-cutting machine. The 
tool we show is a specialized form of that universal 



82 



GEAR-CUTTING MACHINERY. 



machine, adapted particularly to the hobbing of spur 
gears. As may be seen, in form the machine is derived 
from the standard milling machine, bearing about the 
same relation to it that the Becker-Brainard gear cutter 
in Fig. 21 does. The cutter arbor is mounted on what 




Fig. 58. The Reinecker Spur Gear Hobbing Machine. 



corresponds to the work table of the miller, which is 
swiveled so as to bring the teeth of the hob on the upper 
surface parallel to the work spindle. The work spindle is 
driven from the rear of the column by the index worm- 
wheel, which is connected with the cutter spindle through 
change gears (shown at the left of the picture) and the 
splined shafts and bevel gear connections. The knee of 



FORMIXG THE TEETH OF SPUR GEARS. 



83 



the machine having been raised so that the cutter is set at 
tie proper heiglU to cut teeth of the desired depth, and the 
mXe being Btarted, with hob and gear blank rotating 
i Improper ratio, the table with the hob is fed m along 
he knee toward the column of the machine, cutting the 
teeth" the wheel as it does so, the operation being com- 




Fig. 59. 



Ducommun Gear Hobbing Machine. 



pleted when the hob has made one pass through the work 
Ki be noted that the work arbor the knee an he b- 
of the machine are all tied together by a ngid brace, 
which may be adjusted to suit different conditions. 

Ge.« Hobbing M..chines with Cutter Slide on Bed. 

The machine in Fig. 59 is made by the Atelici.de Con- 
struction Mecaniques, ci-<levant Ducommun M too 
Alsace, Germany. It is of the same type, so far as the 



84 



GEAR-CUTTING MACHINERY. 



framework is concerned, as a regular orthodox gear cut- 
ter, it being almost identical in its lines with those shown 
in Figs. 22 to 31 inclusive. The differences in mechanism, 
of course, are those due to the necessity for connecting the 
work spindle and the cutter by change gearing to give 
the proper ratio, and for setting the spindle, as well, at the 
proper angle to agree with the helix angle of the hob. 
The feed, also, is continuously forward until the work is 
completed, instead of having a quick return for each tooth 




cut. 



Fig. 60. Junghans Spur Gear Robbing Machine. 
It is readily seen that this rearrangement means, on 



the whole, a somewhat simpler machine in the case of the 
hobbing machine than for the automatic gear cutter, par- 
ticularly since intermittent indexing is avoided. An 
added complexity is, however, given to this particular 
design by the provision of mechanism for cutting helical 
gears by the formed cutter process. (As in Fig. 107.) 
Another hobbing machine, built by Wilhelm Junghans 



FORMING THE TEETH OF SPUR GEARS. 85 

Werkzeugmaschincnfabrik, Chemnitz, Germany, has the 
base and column in one solid casting (see Fig. GO). It is 
also provided with elaborate rim and work supporting 



Fig. 61. The Wanderer Spur Gear Hobbing Machine. 

arrangements, there being an outboard bearing for the 
spindle, and rim supports both front and back. This 
machine is designed for hobbing spur and worm gears. It 
is also provided, when so desired, with hand indexing 
mechanism for cutting spur gears with formed cutters. 



86 



GEAR-CUTTING MACHINERY. 



A third example of this construction, more strongly 
resembling the orthodox gear cutter than either of the 
others, is illustrated in Fig. 61. A type of drive which 
has been used quite generally for this service is here 
employed. An internal gear of large diameter is mounted 
on the spindle; this is driven by a pinion on a parallel 
shaft, which is, in turn, geared to the short shaft about 
which the angular adjustment of the head is made. The 




Fig. 62. The Farwell Spur Gear Robbing Machine. 

internal gear permits the use of larger and heavier driving 
gearing without raising the cutter spindle unduly above 
the bearings on the bed. This machine is built by the 
Wanderer Works, Schoenau, near Chemnitz, Germany. 

The Standard Form of Hobbing Machine. 

The more usual type of spur gear hobbing machine differs 
from the examples we have just described in the position of 
the spindles. In this case the cutter spindle is mounted in a 
slide on the column, while the work is carried on the bed, 



FORMING THE TEETH OF SPUR GEARS. 



8T 



being adjusted in or out on it according to its diameter. In 
its general arrangement it bears a strong resemblance to the 
standard type of formed cutter machine for heavy work, as 
illustrated in Figs. 33 to 38. The small machine shown in 
Fig. 62 is of this construction. It is built by the Adams 
Company, Dubuque, Iowa. The simplicity of its design is 




Fig. 63. The Gildemeister Gear Hobbing Machine. 

at once evident. The belt drive permits the required angular 
drive of the spindle, and the connection with the work table 
through the change gears is reduced to the fewest possible 
parts. The feed of the cutter slide on the column is operated 
by an adjustable ratchet mechanism. 

A larger machine of the same type,, built by Gildemeister 
& Co., A. G., Bielefeld, Germany (see Fig. 63), is of the 
more usual form in which the base is carried clear down to 
the floor. Fig. 107 shows this machine cutting a spiral gear 



88 



GEAR-CUTTING MACHINERY. 



with a formed cutter. This operation requires very httle 
change in the mechanism needed for straight spur gear hob- 
bing. The wide provision of this arrangement on European 
machines is doubtless due to the patent restrictions on the 




Fig. 64. An Electrically-driven Gear Robbing Machine built by 
Humpage, Thompson & Hardy. 



spiral gear bobbing process, which is described later. It is 
interesting to note the resemblance between this machine 
and the American-built one in Fig. 118. 

In Fig. 64 is a machine built by Humpage, Thompson & 
Hardy, of Bristol, England. It appears to be of unusually 
heavy construction. The machine as shown is entirely 



FORMING THE TEETH OF SPUR GEARS. 



89 



self-contained, a motor being mounted on top of the column. 
It can be made either motor or belt driven without other 
alteration than the removal of the motor and gears and the 
substitution of a pulley^ or vice versa. The drive is of the 




Fig. 65. The " Rhenania " or " Burton " Spur Gear Robbing Machine. 



constant speed type, the speed changes being obtained 
through gearing running constantly in a bath of oil. The 
machine is provided with an unusually ingenious feed 
mechanism. A pair of taper pulleys, carrying a light belt, 
is used as a primary means of changing the feed. This 



90 GEAR-CUTTING MACHINERY. 

operates, however, through the medium of an epicyclic gear 
arrangement through which most of the strain of trans- 
mission is taken. The cutter slide is overbalanced, so that 
it has to be feci against the pull of the counterweight, thus 
taking up all back lash. 

The machine shown in Fig. 65 is sold on the continent by 
Alfred Schiitte, and there known as the ''Rhenania." In 
London, England, it is sold by Burton, Griffiths & Co. and 
called the "Burton." This is one of the machines which 
can be furnished for cutting spiral gears if desired, though 
in the form shown it is adapted for spur gears only. The 
spindle of this machine is driven somewhat differently from 
the previous ones shown. A worm connected at its inner 
^nd by bevel gears to the vertical power transmission shaft, 
and located on the axis of the angular adjustment, drives a 
worm-wheel on the short shaft mounted above and to the 
rear of the cutter. Spur gears connect this short shaft with 
the spindle. The work table may be revolved freely in set- 
ting the work by withdrawing the index worm, this being 
mounted on a dovetail slide, which is withdrawn or inserted 
again by operating the square-head collar screw shown. 
Adjustable stops limiting this motion determine its adjust- 
ment, which may be altered to compensate for wear. The 
worm is of hardened steel, ground all over after hardening. 
The work spindle may be supported, w^hen necessary, by a 
stiff outboard bearing on an arm which is fastened to the 
back of the table and the back of the bed, tying the work, 
work table, and bed rigidly together. 

Another machine of German origin, made by the Schubert 
& Salzer Maschinenfabrik, of Chemnitz, and sold by Selig, 
Sonnenthal & Co., of London, England, is shown in Fig. 66. 
This machine, like many of the others, has the spindle driven 
by an internal gear. To allow this to be made of unusually 
large diameter and still bring the hob as close to the face of 



FORMING THE TEETH OF SPUR GEARS. 91 




Fig. 66. A Continental Gear Robbing Machine, sold by Selig, 
Sonnenthal & Co. 



the column as possible, so as to give a rigid construction, the 
hob is carried below the axis around which the swiveled head 
is adjusted, instead of centrally with it, as is usually the 



92 



GEAR-CUTTING MACHINERY. 



case. This limits the adjustment to the comparatively 
sUght angle required for spur gears, but' it would seem to 
greatly increase the stiffness of the construction and the 
power of the drive. As may be seen, the outboard support 
for the work arbor is of unusual design, consisting of an arm 
bolted to the side of the column, carrying a slide which may 
be adjusted in or out to suit the position of the work table. 




Fig. 67. The Wallwork Gear Hobbing Machine. 



The machine shown in Fig. 07 is built by Henry Wallwork 
& Co., Ltd., Manchester, England, and sold by Alfred Her- 
bert, Ltd., Coventry, England. A number of interesting 
features will be noted in this machine. The spindle drive, 
for instance, is unusual. A train of spur gears connects 
the shaft on the axis of the swiveHng adjustment with a 



FORMING THE TEETH OF SPUR GEARS. 93 

short vertical shaft which (h'ives the cutter arbor by worm 
or spiral gearing. The work support consists of a triangular 
arm supported by two vertical posts, the outer end of the 
arm having a bushing for the work arbor. One of the ver- 
tical posts is longer than the other, and the arm may be 
raised from the shorter one and swiveled about the longer 
one when removing or replacing the work. Since this sup- 
port always travels with the table it does not have to be 
adjusted when adjustments are made in the position of the 
latter. The table has a large annular bearing, with an 
extended shank having a tail bearing fitted with lock nuts 
to prevent lifting. The chip pan is solid with the slide and 
does not rotate with the table as in some of the other 
machines. 

HoBBiNG Machines with Adjustable Spindle 

Column. 

The machine in Figs. 68 and 69 (Sir W. G. Armstrong, 
Whitworth & Co., Ltd., Manchester, England) belongs with 
the machines just described, but is differentiated from them 
by the fact that the column carrying the spindle is adjusted 
on the bed for the diameter of the work, instead of having 
the work table adjustable. In this respect it resembles the 
gear cutters shown in Figs. 39, 40, and 41. Since the work 
spindle is stationary, the index wheel is placed below the 
bed. The spindle drive is through spur and bevel gears 
from the vertical shaft alongside the column. This machine 
is so large that special provision is made for handling most 
of the movements, there being a power elevating device for 
the spindle head, and a power traverse of the head on the 
bed. As shown, also, the spindle head is swiveled by a 
worm meshing with worm-wheel teeth cut on a portion of 
the periphery of the sector. 



94 



GEAR-CUTTING MACHINERY. 



^jT^-. 






mm mmmm BFv^ 




i!^ > J 



^fe'Ai " "" : 



Fig. 6S. Armstrong-Whitworth Hobbing Machine, with Column 
Adjustable for Diameter. 



PHANGE WHEELS 
TO SUIT PITCH 
OF GEAR BEING 
CUT 



TO CHANGE 
VERTICAL FEED 




Fig. 69. End View of Armstrong-Whitworth Machine. 



FORMING THE TEETH OF SPUR GEARS. 



95 



In Fig. 70 is shown a gear hobbing machine of this type 
made by Maschinenfabrik Lorenz, Etthngcn, Baden, Ger- 
many. The machine is made in several sizes. The exam- 




FiG. 70. Lorenz Gear Hobbing Machine. 



pie shown, which is next to the largest size, wiU take work 
up to 110 inches in diameter. It is of very attractive de- 
sign, and is provided with unique mechanism for spiral gear 
cutting, which will be described later. The stationary 
location of the work spindle with reference to the bed 
should permit of a stiff construction at this point. 



96 



GEAR-CUTTING MACHINERY. 



Gear Robbing Machine of Special Design. 

A machine which cannot be classified with any of the 
previous examples is shown in Figs. 71 and 72. The main 




Fig. 71. Reynolds Machinery Company's Automatic Spur Gear 

Hobbing Machine. 

feature of novelty in its construction is plainly seen in the 
top view; the cutter slide has no swiveling adjustment, 
but is set permanently at a definite angle with the work 



FORMINCx THE TEETH OF SPUR GEARS. 97 

spindle. This is made possible by the fact that the angle 
of the thread on all the hobs used is the same, the diameter 
of each being so proportioned to the pitch as to effect this. 
The driving pulley is geared directly to the hob spindle. 




Fig. 72. Top View of the Reynolds Hobbing Machine. 

Change gears connect the outer end of the spindle with a 
worm-shaft, by means of which the work spindle gear is 
driven. This gear has straight, spur gear teeth, so that it 
may be fed forward as the work is fed over the hob, with- 
out requiring the usual splined connection. The worm shaft 
is at an angle, being parallel with the cutter spindle, and the 
worm is so proportioned that this is its proper angle for 
engagement with the teeth of work driving gear. 



98 



GEAR-CUTTING MACHINERY. 



Of course the pitch diameter of a hob is larger when it is 
new than when it is old, so that the slide should, theoreti- 
cally, be set at a slightly different angle as the diameter 
changes. It is a question if this slight change makes any 
practical difference. In any case the principle of the 
constant angle for a series of hobs of different pitches is an 
interesting and important one. This machine is built by 
the Reynolds Machine Company, Rock Island, 111. 




Fig. 73, The Cutter Controlling Mechanism of the Swasey Hobbing 

Machine. 

An ingenious hobbing machine was built a number of 
years ago by the Warner & Swasey Company, Cleveland, Ohio. 
Instead of using a worm-shaped hob, the hob was formed 
of a series of formed rack cutters made in two halves, which 
were shifted endwise with relation to each other by a cam 
mechanism. In Fig. 73 one half of the ''hob" is shown 
at A, and the other at B. The two halves of the cam 
controlling the two sections of the hob are at G and G\ 
This split hob and the blank are geared to rotate together 



FORMING THE TEETH OF SPUR GEARS. 99 

the same as in other hobbing macliines. The half of the 
hob, A, which is cutting is fed forward by the cam to cor- 
respond with the rack movement required by the rotation 
of the blank. When this half of the hob has left the 
cut it is rapidly returned by the cam, ready to start in 
on its forward axial movement as soon as it again reaches 
the cutting position. Meanwhile B is cutting, and this 
too is drawn back as soon as it goes out of action, so as to 
be ready to start in again. Thus, by the alternate sliding 
on each other of these two halves, this split circular hob, 
set with its axis at right angles to that of the work, gives 
the same cutting action as the helical hob in Fig. 56, with 
its axis set at an angle. 

It will be seen that the list of hobbing machine buiklers 
is quite an imposing one, including (see also Figs. 117 
to 128) twenty four manufacturers of these machines. 
With the exception of the Reinecker machine, which dates 
from an earlier time, all of these were designed within the 
past few years, most of them to meet the demand for 
gear-cutting machinery created by the automobile trade. 

The Grinding or Abrasion Operation applied 
TO THE Molding-Generating Process. 

One appHcation of the molding-generating process involv- 
ing the grinding operation uses the rack tooth principle in 
a manner exactly identical with that shown in Fig. 10, in 
forming the cutters used with the Fellows system of gear 
tooth shaping. A special machine is provided, carrying an 
emery wheel with a plane face which can be constantly 
kept straight by means of a diamond truing device incor- 
porated in the machine itself. The hardened gear cutter, 
which has been cut to leave but a few thousandths of 
metal to finish on the sides of the teeth, is placed in the 



100 



GEAR-CUTTING MACHINERY. 



machine and rolled past the face of the emery wheel under 
the restraint of metallic tapes in a way that is similar to 
that shown in Fig. 10. 
An application of tliis principle to the finishing of the 




Fig. 74. A Machine for Grinding the Teeth of Gears 
to Accurate Shape after Hardening. 



teeth of hardened gears is shown in Figs. 74 and 75. This 
machine trues the teeth of hardened gears used in automo- 
bile construction. The principle of its action is also 
the same as in Fig. 10, though carried out in a somewhat 
different way than in the case of the Fellows cutter grinding 



FORMING THE TEETH OF SPUR GEARS. 101 

machine just mentioned. In this case the emery wheel 
has its outUne beveled to the shape of the rack^ tooth, 
using for this purpose both sides of the wheel, which has 
an outline more nearly resembling the shaper tool T^ in 
Fig. 8 than the grinding wheel of Fig. 10. Attachments 
permanently set to the proper angle (14^ 15 degrees, or 
any other angle desired) are provided, by means of which 
the operator can almost instantly bring the wheel to the 
proper shape whenever it shows signs of losing it. The 




Fig. 75. Another View of the Machine shown in Fig. 74. 

emery wheel has a continuous vertical reciprocating move- 
ment, great enough to cover the whole face of the wheel. 
It will be seen that it is thus made to cover the whole 
surface of the rack tooth which it represents in the molding- 
generating process. 

The hardened gear to be operated on, previously cut 
to leave a few thousandths for finishing, is mounted on the 
vertical work arbor on the table as shown. By suitable 
change gears and controlling mechanism, this sUde is 
made to travel across the face of the wheel while the work 



102 GEAR-CUTTING MACHINERY. 

is rotated at the same time, in such a ratio as to give the 
identical movement that would result from rolling the 
wheel on the imaginary rack, a tooth of which is represented 
by the outhne of the emery wheel. The work starts in at 
one side of the wheel, out of contact with it, rolls into it 
until the grinding wheel is in action, passes by to the 
further side, and returns to its first position, thus finishing 
one tooth space to proper form. An automatic indexing 
mechanism (adjustable for any number of teeth between 
12 and 60 inclusive) then indexes the wheel one space, and 
it again rolls along the front of the emery wheel and returns, 
thus finishing another tooth space. This operation is 
repeated automatically until the whole gear has been 
ground. The diameter of the wheel used is 12 inches. 
The maximum diameter of gear which can be finished is 
llf inches with a 2-inch face. This machine, which is 
built by J. E. Reinecker of Chemnitz-Gablenz, Germany, 
is sold by E. Chouanard, 3 Rue Saint-Denis, Paris, and 
by C. W. Burton, Griffiths & Co., Ludgate Square, London. 
Mention might be made here of a rather unusual exten- 
sion of the bobbing process, and one which at first thought 
would seem to be impracticable. This is reported in a 
paper read before the British Institution of Mechanical 
Engineers in July, 1908, on "The Evolution and Methods 
of Manufacture of Spur Gearing, '' by Mr. Thomas Humpage, 
the maker of the bobbing machine illustrated in Fig. 64. 
Mr. Humpage relates that he has experimentally built 
and used a corundum ''hob" for finishing gears on which 
a few thousandths had been left for grinding. In using 
these hobs or worms, the tool is adjusted axially so that one 
side of the thread touches one side of the teeth of the work. 
The wheel is then fed down automatically, grinding one 
side of all the teeth and generating them to the finished 
form. The machine is next stopped, the wheel raised by 



FORMING THE TEETH OF SPUR GEARS. 103 

hand, and a finishing cut taken. The other sides of the 
teeth are then ground and finished in the same way. 
Mr. Humpage proposes to make a macliine using a hob 
of this kind in which a device hke that on the fly-tool 
worm-wheel hobbing machines (see Fig. 141) will be used 
for traversing the hob to distribute the wear across its 
length. It is found that the wear on the hob is very 
shght, being about a thousandth of an inch in the worn 
part for cutting a 70-tooth, 7-pitch, IJ-inch face cast-iron 
wheel, which was finished in eight minutes. In the com- 
plete machine the author proposes to mount a corundum 
wheel for truing up the worm. He suggests also, that this 
finishing process should be applied to all gears, whether 
soft or hardened. 

This completes the description of machines for forming 
the teeth of spur gears. 



CHAPTER IV. 

MACHINES FOR CUTTING THE TEETH OF INTERNAL 
GEARS AND OF RACKS. 

As has been stated, the internal gear is akin to the spur 
gear, and the machinery for cutting it acts on practically 
the same principles, except as limitations are imposed by 
the concavity of the surface in which the teeth are cut, 
as compared with the convex shape of external gearing. 

Machines and Attachments for Cutting Internal 
Gears by the Formed Cutter Principle. 

For cutting internal gears, the formed tool method is 
the most obvious and the most commonly used. The teeth 
may, for instance, be cut by a shaper tool with a projecting 
head, formed somewhat after the fashion of the tools used 
for cutting key ways in the hubs of pulleys, etc., the work 
being mounted on the face-plate of an indexing fixture 
on the table of the shaper, slotter, or planer. One job 
came to the writer's notice in w^hich the work was fastened 
to a face-plate on the spindle of an ordinary automatic 
gear-cutting machine, while the shaping tool was operated 
by a shaper bodily lifted to a position on the bed of the 
gear cutter and clamped in place there. In such cases 
the rnovements are, of course, largely controlled by hand, 
the tool holder being fed down into the work by the 
operator. 

Most machines for internal gears use the formed milling 
cutter to shape the teeth. A common method of using 
this process employs an attachment to the regular auto- 

104 



CUTTING INTERNAL GEARS AND RACKS. 105 

matic spur gear cutting machine, carrying the cutter on a 
projecting arm adapted to enter t\u) internal gear and 
work on its inner periphery. An example of this is seen 
in Fig. 76, which shows the attachment provided by 
Gould & Eberhardt, of Newark, N. J., for cutting internal 
gears on their regular spur gear cutting machine. The 
cutter is driven by a train of spur gears from a driving 




Fig. 70. Attachment to the Gould & Eberhardt Gear Cutter for 
Cutting Internal Gears. 

gear on the regular cutter arbor. The pivots of these 
gears are shown by the projecting ends of the studs on 
which they run. While this arrangement furnishes a 
practical and much-used means for cutting internal gears, 
it is evident, of course, that it is not possible to take quite 
so heavy cuts as when cutting spur gears, on account 
of the indirectness of the means by which the cutter is 
driven, and the necessarily small diameter of the gear from 
which it receives its motion. 



106 GEAR-CUTTING MACHINERY. 

An attachment of a very similar kind, modified to suit 
the changed design of the machine, is shown in Fig. 77. 
This is the Atlas gear cutter shown in Fig. 36. As may 
be seen, the attachment is bolted to the face of the 
cross rail, and is fed down into the work in the same way 
that the attachment in Fig. 76 is fed forward into it. 
Other manufacturers make similar devices for use with 
their machinery. 

In Fig. 78 is shown a machine of great capacity, arranged 
for the cutting of both internal and external spur gear 




Fig. 77. The Atlas Machine as arranged for cutting Internal 
Gears; compare with Fig. 36. 

segments. As posed, it is cutting internal teeth. The 
work is mounted on a sector pivoted at the left-hand end 
of the bed, and having gear teeth cut in its periphery, by 
which it is indexed. The work is clamped to this sector at 
the ' proper distance from the pivot to give the radius 
desired. The cutter shde operates on vertical ways on a 
carriage carried by the cross rail. Two cutter spindles 
are provided, one on the right and the other on the left 
hand side of the cutter head, one being used for internal 
and the other for external gears. The movement is 



CUTTING INTERNAL GEARS AND RACKS. 



107 



brought to the spindles through a train of spur and bev(4 
gears as shown. This machine, which was designed 
primarily for dealing with gear segments for gun mountings, 




Fig. 78. Armstrong- Whitworth Machine for cutting Internal or 
External Teeth in Segments of Large Diameter. 



will cut teeth in segments having an extreme radius of 
13 feet and a face of 12 inches. It is automatic in all 
its movements, including the dividing mechanism. Sir 
W. G. Armstrong, Whitworth & Co., of Manchester, 
England, are the builders. 



108 



GEAR-CUTTING MACHINERY. 



Cutting Internal Gears by the Molding-Generating 

Principle. 

The Fellows system of gear cutting, previously illus- 
trated in Fig. 55, is perhaps the most striking method of 




Fig. 79. The Fellows 36-Inch Gear Shaper at work on an 

Internal Gear. 



cutting internal gear teeth. The machine shown in Fig. 79 
is forming the teeth in an internal gear. The process, which 
belongs to the molding-generating order, is exactly identical 
to that employed for external spur gears, the cutter and 
work being geared to rotate together in the proper ratio. 



CUTTING INTERNAL GEARS AND RACKS 109 

It has a number of advantages over the formed cutter 
method. It does not require the exaggerated clearance 
at the bottom which the rotary cutter needs for running 
out into. The cutting tool works to as good advantage 
as when cutting external gears. No change in the 
machine is necessary, and special cutters are not required, 
the same tool being used as in cutting an internal gear of 
the same pitch. The ease with which internal gears may 




Fig. 80. An Attachment for bobbing Internal Gears. 



be cut with this machine, and the fact that it is quite 
generally used for this work, have encouraged the use 
of internal gearing in the past few years for cases in which 
it is better fitted than external spur gearing, but where the 
difficulty of making it would formerly have barred its use. 
Fig. 80 illustrates the surprising operation of hobbing 
an internal gear. This operation bears the same relation 
to the hobbing machine in which it is done that the use 
of the internal gear-cutting attachment shown in Fig. 76 



110 GEAR-CUTTING MACHINERY. 

bears to the orthodox spur gear cutting machine. The 
method of chiving through a train of gearing connecting 
the cutter with the regular spindle is identical. With 
this attachment the hob has a pitch surface of a barrel- 
shaped form, with the radius of curvature corresponding 
with the pitch radius of the wheel to be cut. In producing 
these hobs a master internal toothed wheel is hardened, 
so that the teeth act as cutters. The soft hob blank is 
then placed in the machine the same as when at work, as 
shown in Fig. 80, and a theoretically correct profile is 
generated on it by the hardened internal wheel. The hob 
itself is then relieved, hardened, and ground ready for use. 
It is adapted only to cutting gears of the diameter and 
pitch for which it was made. David Brown & Sons, 
Huddersfield, England, are the originators of this device. 
The odontographic and describing-generating methods 
are as limited in their application to internal gearing as 
to external gearing. The grinding or abrasion, and impres- 
sion operations, also, have seldom, if ever, been applied to 
the cutting of internal gears. 

Formed Tool Rack-cutting Attachments to 
Standard Machines. 

As was the case with internal gearing, the formed tool 
method is the one most largely used for cutting racks. 
The primitive means consists in clamping the work on the 
table of the planer or shaper, and cutting the tooth spaces 
with a properly shaped tool in the regular tool-post of the 
machine. After each space has been cut, the tool-post is 
moved along the proper distance to bring it in position for 
a new space, or, in the case of the shaper, the work table 
is shifted the same amount for the same purpose. A new 
tooth space is then formed as before, and the operation is 



CUTTING INTERNAL GEARS AND RACKS. 



Ill 



repeated until the work is done. In making the measure- 
ments for the amount by which to shift the relative position 
of the work and the tool for each cut, various means may 
be used. A stop may be provided, set ahead of the pre- 
vious position by an amount determined by a gauge of a 
thickness equal to the circular pitch of the tooth being cut. 




Fig. 81. The Rack-cutting Attachment used with the 
Brown & Sharpe MiUing Machine. 



After the adjustment has been made for a new tooth, it 
may again be located in position for the next cut by setting 
to the proper distance away, as determined by the thickness 
of the gauge. If the screw by which this adjustment is 
made is provided with a dial reading to thousandths, this 
may be used. One way is to set the dial carefully to zero 
before making each setting; then operate the screw to move 
the slide the proper amount in thousandths of an inch as 



112 



GEAR-CUTTING MACHINERY. 



determined by the circular pitch of the tooth being cut. 
The dial may then be brought back to zero, repeating the 
operation when the next adjustment is to be made. 

More elaborate means of indexing are provided for 
special rack-cutting machines. The arrangement generally 
used is identical with that shown in Fig. 16 as applied to 
the spur gear cutting machine, excepting that the index 
worm and index wheel are replaced by a lead-screw and 




Fig. 82. Le Blond Change Gear Attachment for Spacing in Rack 
Cutting and Similar Operations. 



nut, which serve to give a longitudinal movement to the 
work table in the same way that the rotary movement 
is given to the work spindle of the gear-cutting machine. 
This longitudinal movement equals the circular pitch, of 
course, and is obtained by using appropriate change gears 
between the one-revolution shaft and the lead-screw. 

In Fig. 81 is shown an attachment for the milling machine 
used for cutting racks. This device, which is applied to the 
Brown & Sharpe milling machines, consists simply of a 



CUTTING INTERNAL GEARS AND RACKS. 



113 



holder clamped to the front of the column and the over- 
hanging arm, and carrying a short cutter spindle at right 
angles and below the main spindle of the machine. This 
is connected to the main spindle by suitable gearing. On 
the projecting end of it a formed cutter of ordinary con- 
struction is fastened. The vise shown in the cut is pro- 




FiG. 83. The Gould & Eberhardt Shaper with Attachment 
for Cutting Racks. 

vided for holding the work. The work may be indexed by 
using the graduated dial as explained, or by making use of 
a change gear attachment, furnished by the makers, 
operating on the principle described in the preceding 
paragraph. 

In Fig. 82 is shown another milling machine having an 
indexing attachment for rack cutting. The feed screw 
of the table is turned by the crank shown. The screw 
is connected by change gearing with a disk carrying a 



114 GEAR-CUTTING MACHINERY. 

notch in which a stationary lock bolt may be seated. 
When this bolt is withdrawn, and the crank is turned 
until the bolt falls into place again, the table is advanced 
a definite amount, equal to the desired circular pitch, as 
determined by the change gears. The cutter driving 
attachment is similar to that in Fig. 81. 

Rack-cutting attachments are made to apply to the 
shaper as well as to the milling machine. An example of 
one made by Gould & Eberhardt, Newark, N. J., is shown 
in Fig. 83. The regular swiveling tool head has been 
removed from the ram, and its place is taken by a casting 
carrying a cutter arbor and the necessary gearing and 
other mechanism for driving it. In addition to this, the 
ram is provided with attachments for giving a gradual 
forward screw feed for advancing the cutter through the 
work, in place of the usual reciprocating movement, which 
is disconnected when the machine is used in this way. A 
suitable vise for the work is clamped on the work table, 
and an indexing arrangement involving the use of change 
gears is provided for shifting the table from one cut to 
another. 

Special Formed Tool Rack-cutting Machines. 

Most commercial rack-cutting machines in their struc- 
tural design are developments of the milling machine idea. 
The automatic rack-cutter for small size and accurate 
work, shown in Fig. 84, is an example of this type. This 
tool is built by Sloan & Chace Manufacturing Company, 
of Newark, N. J. Its resemblance to the milling machine 
and attachment shown in Fig. 81 is obvious. It is auto- 
matic in all its movements, which are mostly cam-oper- 
ated, as is usual in gear-cutting machinery of the precision 
type built by manufacturers of watch- and clock-making 
machinery. 



CUTTING INTERNAL GEARS AND RACKS. 115 

Another machine of this kind is built by Walcott & 
Wood Machine Tool Company, Jackson, Mich. (Fig. 85). 
This machine, as may be seen, involves the same struc- 
tm-al features as the preceding one, but is built for much 




Fig. S4. The Sloan & Cliace Rack Cutter for Small Work. 

larger and heavier work. Its movements are obtained by 
screws and gear-driven mechanisms, instead of by cam 
movements. As shown, the cutter spindle is driven by 
gearing on each side, the main drive on the left being by 
herringbone gears. This tends to give a smoothness of 



116 



GEAR-CUTTING MACHINERY. 



action which the necessarily small diameter of the driving 
pinion would otherwise make impossible. The cutter 
arbor is driven by a tongued connection from each end. 
It is held in position by two bolts passing through the 




Fig. 85. The Walcott & Wood Automatic Rack Cutter. 



driving spindles at each side, which, when tightened 
together, make driving spindles and cutter arbor practi- 
cally a solid piece, giving a very powerful support. There 
being 10 inches of cutter space on the arbor, it is well 
adapted to the use of gang or multiple cutters. Pro- 
vision is made for this in the gearing, there being two sets 



CUTTING INTERNAL GEARS AND RACKS. 117 

of change gears, one of them set for the pitch in the ordi- 
nary way, while the other is set for the number of teeth it 
is desired to index at once. All of the gears shown are 
provided with guards, which have been removed in taking 
the photograph so that the drive may be more easily 
understood. A feature of this machine and the previous 




Fig. 86. The Machine built by vVarner & Swasey Company to 
overcome the Driving Difficulty. 

one is the automatic mechanism provided for throwing off 
the counter-shaft belt shifter when the required number of 
teeth has been cut. 

In the machine shown in Fig. 86, formerly built by 
Warner & Swasey Company, of Cleveland, Ohio, the diffi- 
culty in the driving of the cutter spindle has been inge- 
niously overcome. The cutter spindle has been extended 
to great length at the left side of the machine, where it is 



118 GEAR-CUTTING MACHINERY. 

driven by a gear of as large diameter as is necessary to give 
it a powerful yet smooth and even movement. Of course 
the capacity of the machine for cutting racks is limited to 
the length from the cutter to the face of the driving gear. 
This is beyond the extreme indexing range of the table 
anyway, but the possible range may be doubled by cut- 
ting half the rack, and then reversing it so that the over- 
hang of the work is at the right end of the table. The 
efhcacy of this method of driving the spindle in avoiding 
some of the difficulties inherent in the rack cutter may be 
vouched for from the fact that the idea in a modified form 
has been appHed to all the rack cutters of various types in 
the plant of one of the largest firms making a special busi- 
ness of cutting gear teeth. 

As the rack-cutting machines just described are derived 
in form from the milling machine with rack-cutting attach- 
ment, so a machine may be made resembling in its move- 
ments the arrangement shown in Fig. 83, in which the 
cutter spindle is mounted on a shaper ram, which is fed 
forward bodily to pass the cutter through the work. One 
machine in very common use built on this plan is the 
Pratt & AMiitney rack cutter. This firm is no longer 
building this machine, so we do not show a cut of it here, 
though it is of common occurrence and familiar to every 
one engaged in the business. Another machine of the 
same type, built by the R. K. Le Blond Machine Tool 
Company, is shown in Fig. 87. This w^as for use in the 
shops of the builders. It is a rugged, compact machine, 
fully automatic, with a single pulley drive. All the changes 
of speed, feed, and indexing are effected by change gears. 

A third form in which the rack-cutting machine is built 
resembles in its construction the heavy type automatic 
gear cutter, such as that built by Craven Brothers and 
shown in Fig. 39. The only difference is in the substitu- 



CUTTING INTERNAL GEARS AND RACKS. 



119 




o 

^-1 






O 



a} 



a 

a 

o 
Q 



o 



fc/0 



:3 
o 
I 

o 



00 

6 



120 



GEAR-CUTTING MACHINERY. 



tion of a longitudinal work-carrying slide and indexing 
mechanism for the rotary work spindle and indexing 
wheel of the spur gear machine. This likeness may 
easily be traced in the case of the Gould & Eberhardt 
rack cutter, shown in Fig. 88. As in the spur gear 
machine, the spindle is mounted on a head sliding on ver- 
tical ways on the face of a column. This column may be 
adjusted in and out on the bed to suit the thickness of the 




Fig, 88. A Large Size of the Line of Gould & Eberhardt Rack- 
cutting Machines. 



work being operated on. The table, which takes the 
place of the spindle and face-plate of the spur gear 
machine, slides on ways on the main body of the bed. It 
will be noted that these ways are of unusual length, sup- 
porting the table well, even when it is moved out to the 
extreme of its travel in either direction. The change gears 
regularly furnished permit the cutting of either diametral 
or circular pitches. The table can be geared to index in 
either direction. The work may be fastened either directly 



CUTTING INTERNAL GEARS AND RACKS. 



121 



to the table by the T-slots provided or may be clamped in 
the angle vises shown. The cutter spindle is of chrome 
nickel steel, strongly gear-driven, by worm and worm- 
wheel and spHned shafts. The holding of the blank in a 
vertical position, and the vertical travel of the cutter 
slide, permit a rigid support for the work against the 
thrust of the cut, besides causing the lubricant and chips 




Fig. 89. The Reinecker Automatic Rack Cutter. 



to drop freely out of the way. This type of machine is 
convenient for setting, inspecting, and testing the work. 

The machine built by J. E. Reinecker, of Chemnitz- 
Gablenz, Germany, shown in Fig. 89, like the preceding 
one, is entirely automatic in all its movements, though it 
is furnished, if desired, in semi-automatic form. After the 
rack is cut through, a special arrangement returns the 
table to its starting position. This is of great advantage 
when stocking and finishing cuts are made, as the dividing 



122 



GEAR-CUTTING MACHINERY. 



follows the same direction and from the same starting 
point. 

The driving difficulty previously mentioned as being 
met with in the rack cutter is overcome in this machine in 
a novel manner — see the line drawing, Fig. 90. As there 
shown, the cutter spindle is- set on an angle with the work, 
and the forms of the cutters used are made to suit; that is 
to say, the formed tools used in shaping them are set at 
the same angle as that given to the axis of the cutter 
spindle. This arrangement obviously allows the use of a 




90. Diagram showing Angular Position given the Spindle of the 
Reinecker Rack Cutter to obtain Large Driving Gear at C. 



driving gear C considerably larger in diameter than the 
cutters. The drive is from a vertical shaft D, through a 
bevel pinion to bevel gear A, driving pinion 5 meshing with 
gear C on spindle E. As here shown, there are two rough- 
ing cutters F, and two finishing cutters G. Of course the 
angularity of the spindle necessitates an increase in diam- 
eter for each succeeding cutter on the arbor. 

This scheme is especially interesting to the writer 
because a similar suggestion occurred to him at one time 
in conversation with the designer of the machine shown 
in Fig. 87. In talking the matter over, however, the 
arrangement seemed inadvisable, owing to the necessity 



CUTTING INTERNAL GEARS AND RACKS. 123 

for special cutters and the added complexities of using 
them in gangs as here shown. Besides this, it would prob- 
ably be impossible to cut cycloidal teeth of accurate form 
by this method, because it would be impossible to obtain 
clearance for the sides of the cutters at the pitch hne, 
where, when theoretically correct, the sides of the teeth 
are parallel for an infinitesimally small distance. For 
involute cutters, also, it is obvious that the angle made by 




Fig. 91. Planer Type Automatic Rack Cutter, built by 
G. Wilkinson & Son. 



the axis of the spindle with the face of the rack must not 
exceed the number of degrees in the pressure angle (or 
angle of the sides of the teeth) of the rack being cut. Mr. 
Reinecker appears to have found this method commer- 
cially successful, however, and an actual trial of it is the 
only true test in a case of this kind. 

The rack cutter shown in Fig. 91, built by G. Wilkinson 
& Son, Keighley, England, is built after the planer pattern. 
The cutter head is mounted on a slide on the cross rail, on 



124 



GEAR-CUTTING MACHINERY. 



which it travels as it is fed through the work. The work 
is clamped to the platen of the machine, which is indexed 
longitudinally for the spacing of the teeth. The indexing 
is done by hand, though the mechanism for moving the 
table is not released until the slide has been returned to 




Fig. 92. Heavy Automatic Rack-cutting Machine of the Open-side 
Planer Type, buiU. by Walcott & Wood. 



cut a new tooth, this being done automatically, so that 
there is no possibility of the indexing being done by mis- 
take at the wrong time. The slow forward feed and quick 
return of the cutter slide are automatic. 

Another rack cutter with the structural features of the 
planer is shown in Fig. 92. In the case of this machine it 



CUTTING INTERNAL GEARS AND RACKS. 125 

will be seen that its ancestors belonged to the ''openside" 
instead of to the standard double-housing family of plan- 
ers. The movements are about the same as in the pre- 
vious case, though the machine has an entirely different 
appearance and is built for much larger work. It will cut 
racks up to 1 diametral pitch, 10 inches width of face, 




Fig. 93. Armstrong- Whitworth Automatic Rack Cutter. 

96 inches long, at one setting. For 1 diametral pitch racks 
the machine will take one roughing and one finishing cut- 
ter. For finer pitches, cutters are used in gangs, as shown 
in the engraving, up to the full width of space on the cut- 
ter arbor. The table is provided with a quick return, 
operated by power. The machine is regularly made full 
automatic, but may be furnished in the half- automatic 



126 GEAR-CUTTING MACHINERY. 

style if desired. It is built by the Walcott & Wood 
Machine Tool Company, Jackson, Mich. 

The rack cutter shown in Fig. 93 is built by Armstrong, 
Whitworth & Co., of Manchester, England. The arrange- 
ment of the movements is somewhat different from any of 
the others we have considered. The cutter spindle, as may 
be seen, is driven by a worm and worm-wheel. The feed is 
effected by the forward movement of the cutter sHde on the 
ways provided for it on the rearward extension of the bed. 
The spindle itself is mounted on a bracket, which may be 
adjusted vertically to give the proper depth of cut. One 
interesting feature of this machine is the provision made for 
cutting very long racks by shifting the position of the work 
in the vise when the full range of indexing movement has 
been exhausted. The central vise indexes step by step, 
being under the control of the indexing mechanism. The 
short end vises are screwed to the bed and do not move, the 
clamp screws with which they are provided being loosened 
while the work is being indexed. These end vises are used, 
in shifting the work, to hokl it, while the central vise is 
loosened and returned to the starting point for a fresh grip. 
The particular machine shown is a somewhat specialized 
form, built for cutting racks used in wire fence knitting 
machinery. 

The Molding-Generating Method applied to 
Rack Cutting. 

Besides the formed tool method, the only other one com- 
mercially applied to rack cutting is the molding-generat- 
ing method. The only example of this is in the Fellows 
system of gear shaping, which is appUcable to the cutting 
of racks as well as to making spur and internal gears. The 
Fellows gear shaper as arranged for rack cutting is shown 



CUTTING INTERNAL GEARS AND RACKS. 127 



in Fig. 94. 



This is a smaller size machine than the one 
shown in Fig. 79 cutting internal gearing, and the arrange- 
ment of its parts is somewhat different. In principle, 




Fig. 94. The Fellows Gear Shaper, with Rack-cutting Attachment. 

however, it is identical, the same cutter being used and the 
cutter and work being connected together in the same way. 
The face-plate or other work-holding device for spur gear- 
ing is removed, and in its stead is placed a pinion, firmly 



128 GEAR-CUTTING MACHINERY. 

fixed in the tapered hole of the spindle. A rack-cutting 
attachment is clamped to the machine, consisting of a guide 
provided with horizontal ways on which travels a work- 
holding carriage, having a rack in position to engage the 
teeth of the pinion clamped in the spindle. The vertical 
face of this slide forms a lengthened vise in wliich the work 
is held. 

The method of operation is easily understood. If the 
spindle (and the pinion connected to it, which moves the 
work longitudinally) is geared in the proper ratio with 
the cutter, the machine may be started up with the cutter 
at the starting point, when the latter will roll on the work, 
exactly as if it were a pinion and the work were a rack with 
which it engaged. Under these circumstances the shaping 
action of the cutter will form rack teeth in the work, of suit- 
able shape to mesh with all the gears in the series to which 
the cutter belongs. The operation is the same as shown in 
Fig. 8, except that it is reversed. Instead of having the rack 
the cutting tool and the gear the work, the gear is the cut- 
ting tool engaged in forming teeth in the rack. In addition 
to using an attachment to the regular machine, as in this 
case, the Fellows Gear Shaper Company, Springfield, Vt., 
have made special rack cutters involving this principle, in 
which the work table sHdes on a long bed, as in Figs. 87, 88, 
and 89. 

This completes the description of machines for cutting 
the teeth of internal gears and racks. 



CHAPTER V. 

MACHINES FOR CUTTING THE TEETH OF WORMS AND 

HELICAL GEARS. 

Spiral gearing, twisted and herringbone gearing, and 
worm gearing are all radically different in their action. Tlie 
first two forms, however, and the worm member of the 
third, are identical so far as the principles governing the 
forming of their teeth are concerned; so we will consider 
them together in this chapter. It might be mentioned in 
connection with the name "spiral" gearing that gears of 
this kind are not spiral at all, but helical. A spiral is a 
figure contained in a plane. It resembles the shape of an 
ordinary watch or clock spring, starting from a central point 
about which it circles in widening curves. A hehx has the 
shape of a string wound around a cylinder. The name " hel- 
icaP' has come into common use in describing springs of hel- 
ical shape, and it ought to be used for gears as well. The 
writer would suggest that the reader practice using the term 
'^heUcal gear." Criticism might also be directed toward 
the term "spiral staircase," but since carpentry is out of 
our field, we will not spend any time here in inaugurating 
that reform. 

Almost as great a variety of methods of cutting teeth are 
possible for helical as for spur gears. Commercially, how- 
ever, the formed tool and the mokling-generating principles 
are the only ones of importance. The templet, odonto- 
graphic and describing-generating methods of cutting gear 
teeth (in each of which the outline is worked out by the 
point of a tool, suitably constrained) are most useful for 
cutting gears of large size, in which tools acting on the 

129 



130 GEAR-CUTTING MACHINERY. 

formed tool or molding-generating principle would be sub- 
ject to too heavy cuts. Since helical gearing is generally 
confined to small and medium sized work, these processes 
are unnecessary, being by nature rather slow in action, and 
dependent for their accuracy on the preservation of the 
shape of easily injured points of comparatively small cutting 
tools. As in the case of spur gears, the molding-generating 
method is of comparatively recent introduction, and is 
confined almost wholly to the production of teeth of invo- 
lute form. 

Machines using Formed Tools in a Shaping 
OR Planing Operation. 

With the twisted teeth which we have in gears of the class 
we are discussing, it is evidently necessary, in employing 
shaping or planing operations, to give a rotary movement 
to the blank being operated on, at the same time as, and 
in the proper ratio with, the cutting stroke of the tool. 
This is necessary to compel the tool to follow the helix on 
which the teeth of the gear or the worm are to be formed. 
In Figs. 95 and 96 are shown two attachments for the 
shaper, working on different principles, giving the work 
the proper motion for cutting helical teeth. Both of 
these attachments were built by Gould & Eberhardt, of 
Newark, N. J. 

In the first of these, Fig. 95, the work is mounted between 
centers on a supplementary bed, fastened to the work table 
of the shaper. The face-plate by which the work is driven 
from the head-stock spindle is connected to that spindle by 
an indexing mechanism, consisting of a notched plate, with 
a locking bolt for holding the work in the different positions 
for the different numbers of teeth required. The head- 
stock spindle is connected, by spiral gearing and a set of 
change gears, with a pinion operated by a rack, which rack 



CUTTING WORMS AND HELICAL GEARS. 



131 



is fastened to the shaper ram. It will be seen that this con- 
nection with the shaper ram will give a rocking movement 
to the head-stock spindle and the work, in unison with the 
stroke of the tool. By selecting suitable change gears this 
rocking movement may be made of any desired amplitude 
for a given length of stroke, so that any lead of helix 
desired may be obtained. Provision is made, in the means 

w 

IT 




Fig. 95. Helical Planing Attachment for Gould & Eberhardt Shaper, 
in which the Lead of the Helix is obtained by Change Gears. 



by which the rack is attached to the ram, for raising or 
lowering the work table to the position required for different 
diameters of work. The tool is, of course, fed downward 
by hand, and the indexing is done manually also. On the 
floor at the base of the machine will be seen a pair of right 
and left handed helical gears, similar to the one being 
operated on; the two together form a herringbone gear. 

The second attachment, shown in Fig. 96, employs a radi- 
cally different principle for varying the amphtude of the 



132 



GEAR-CUTTING MACHINERY. 



rocking movement of the head-stock spindle for a given 
stroke of the ram, to obtain different leads of helix. The 
reader, of course, understands that the lead of the hehx is 
the length of the cylinder required to allow a complete 
revolution of the hehx. In this case a spur gear keyed to 
the head-stock spindle meshes with a vertical rack, sHding 
in a guide which is cast integrally with the head-stock. 
This vertical rack is pivoted to a block which shdes in a 




Fig. 96. Helical Attachment for Gould & Eberhardt Shaper, in which 
the Lead of the Helix is obtained by the adjustment of a Swivel- 
ins Guide Bar. 



guide attached to a swiveling head, so that the guide may 
be adjusted to any angle. This swiveling head, in turn, is 
attached to a bar, which is fastened to the ram, and is 
guided on ways supported by a framework at the back of 
the head-stock. It will thus be seen that the forward and 
backward movement of the ram will impart an up and 
clown movement to the rack, which will, in turn, give a 
rocking movement to the spindle of the head-stock and the 
work which it drives. The amplitude of this rocking can be 
increased or diminished by setting the swiveling guide at a 



CUTTING WORMS AND HELICAL GEARS. 133 



greater or less angle, so that the helices of various leads can 
be obtained. This makes the use of change gears unneces- 
sary. The indexing device is similar in principle in the 



two arrangements. 



It will seem strange at first thought, perhaps, to describe 
the cutting of worms in a lathe as an example of the use of 
formed tools in shaping or planing operations, but the oper- 
ation is essentially the same as that shown in Fig. 95. Com- 
pare this with Fig. 97, imagining that the lead-screw shown 
in the latter is of such steep pitch that it can be rotated by 
pushing the carriage backward and forward. Under these 
circumstances, if provision is made for reciprocating the 



e-TOOTH GEAR OR WORM BEING CUT- 




GEARS A,B,C AND D ARE CHOSEN 
TO GIVE THE LEAD DESIRED FOR THE 



DETAIL OF FACE- 
PLATE, SLOTTED 
FOR INDEXING A 
6-TOOTH SPIRAL 
GEAR OR WORM 



SPIRAL GEAR OR WORM 

Fig. 97. The Lathe Method of Planing Helical Teeth in Gears or Worms. 

carriage (corresponding to the ram for the shapcr), the lead- 
screw will be rotated in unison with it, and this movement 
will be transmitted through change gears A, B,C, and D to 
the head-stock spindle, giving a rocking movement to the 
work. The only difference in' the two cases is that in the 
lathe a screw of very steep pitch woukl have to be used to 
change the reciprocating motion of the tool to the rocking 
motion required by the work, while in the case of the shaper 
the more natural rack and pinion movement is employed. 
In the case of the lathe, of course, the power is not 
applied to the carriage but to the spindle. For that reason 
it is best adapted for cutting spiral gears of comparatively 
small lead, or ''worms" as we ordinarily call them. If it 



134 



GEAR-CUTTING MACHINERY. 



were attempted to cut 45-degree spirals, for instance, the 
lead-screw would have to be speeded up so fast, as compared 
with the movement of the spindle, that the driving belt 
would be unable to operate the machine. Special lathes 
have been built for cutting steep worm threads, in which 
the power has been applied to the lead-screw, the spindle 
being driven from it through the change gears. A lathe 
so arranged would have as much difficulty in cutting fine 
pitches as the ordinary lathe does in cutting coarse ones. 




Fig. 98. Automatic Threading Lathe for Worms, made by the Auto- 
matic Machine Company, 

Different methods of indexing may be used for the lathe. 
It will be noticed that in Fig. 97 the face-plate used has the 
same number of slots as the required number of teeth. 
After one tooth space has been cut, the work can be re- 
moved, and replaced again between the centers with the 
tail of the dog in another slot. After this space has been 
completed, the next one is cut, and so on until the whole 
six are finished. Other methods are in use, such as slip- 
ping of change gears A and B past each other a certain 
number of teeth, as determined by calculation. 



CUTTING WORMS AND HELICAL GEARS. 135 

Special lathes are built for threading, some of which are 
automatic in their action. One of these is shown in Fig. 98. 
It is built by the Automatic Machine Company, Bridgeport, 
Conn. The size shown is especially adapted to cutting 
worms. It is provided with mechanism for duplicating the 
action of a manually operated lathe engaged in threading. 
After a piece of work has been placed between the centers 
and the machine has been started, the work revolves, and 
the carriage feeds forward until the proper length thread has 
been cut; then the tool is withdrawn, and the carriage returns 
to begin again on a new cut — and so on without atten- 
tion from the operator. The tool is fed in a certain suitable 
amount at the beginning of each cut, the amount of this 
feed being automatically diminished to give a fine finish 
for the final cuts. When the depth for which the tool has 
been set is reached the operation of the mechanism is 
automatically arrested. In cutting multiple threaded 
worms in this machine multiple tools may be used, thus 
avoiding the necessity for indexing the work. As many 
as eight cutting tools have been used at once on this 
machine, giving a total length of cutting edge of 8 inches. 

Standard Machine Tools using Formed 
Milling Cutters. 

We have spoken hitherto of the formed tool or cutter 
method of shaping the teeth of gears as being one in which 
the tool accurately reproduces its shape in the tooth space 
it forms. This is true in cutting straight tooth spur gears 
and in planing the teeth of spiral gears by the process just 
described. It is not exactly true, however, of any possible 
process of milling spiral teeth. This is best seen in Fig. 99. 
In the three cases here shown we have, first, a planer tool; 
second, a disk milUng cutter; and third, an end milling 



136 



GEAR-CUTTING ]\IACHINERY. 



cutter — all formed to the same identical outline and cut- 
ting helical grooves of the same lead and depth in blanks of 
the same diameter. The section in each case is on the plane 
normal to the hehx at the pitch Hne. (Of course the true 
section to take would be that of the helicoid normal to the 
heUcoid of the groove being cut. The plane in which we 
have taken the section, however, so nearly approximates 
this hehcoid that the error is neghgible.) 



ALL SECTIONS TAKEN ON LINE X-X 




EXACT REPRODUCTION 



APPRECIABLE ERROR 



INFINITESIMAL ERROR 



Fig. 99. Comparison of the Accuracy of Form Reproduction obtain- 
able by Formed Planing Tool, Formed Disk Cutter, and Formed 
End Mill. 



The planer tool necessarily cuts a groove of the same 
shape as its outhne, the plane of its outline being the same 
as the plane of the section shown. The disk milHng cutter, 
however, interferes with the sides of the groove it cuts. 
This interference takes place on one side as the teeth are 
entering, and on the other as the teeth are leaving. This 
results in a generating action which takes place in addition 
to the simple forming action, so that the tooth cut is not an 
exact duphcate of the outhne of the cutter. In the case of 



CUTTING WORMS AND HELICAL GEARS. 137 

the formed end mill there is also an interference of the same 
kind as with the formed disk cutter, but it is so sHght as to 
be absolutely undetectable in all ordinary cases. We only 
know of its presence from theoretical considerations. 

In spite of its imperfect reproduction of the desired form, 
the disk cutter is the type generally used for milling, since 
it may be so relieved as to retain its shape even after re- 
peated grinding. The end mill type of formed cutter can- 
not remove so much stock in a given time, and it is difficult 
to make it so that it can be ground without changing its 
form. The only way in which this grinding can be practi- 
cally performed is by the use of some form of grinding 
machine, in which the wheel is guided by a templet to 
grind the desired form. The formed end mill is used to a 
limited extent, nevertheless. 

The simplest way of using the milling process for cutting 
helical gears or w^orms makes use of the universal milling 
machine. With this machine the work, and the feed-screw 
of the table on which it is mounted, are so connected by 
means of gearing that the forward feeding gives a rotary 
movement to the work, producing a helix of the required 
lead. The mechanism is identical in principle with that 
shown in Fig. 97 for the lathe, and in Fig. 95 for the shaper, 
the only difference being that in the milling process the 
longitudinal movement is a steady feeding motion, made 
once for each tooth space, instead of being a continuously 
reciprocating motion, as in the previous cases. The simple 
indexing devices shown in Figs. 95 and 97 are replaced by 
the more elaborate index plate and worm-wheel device of 
the spiral head. 

This mechanism, as exemplified in the Brown & Sharpe 
universal milling machine with its spiral head, etc., is illus- 
trated in Fig. 100. The work has to be swung at an angle 
with the cutter to agree with the helix angle at the pitch 



138 



GEAR-CUTTING MACHINERY. 



line, as indicated. This is done by swiveling the table of 
the universal milling machine to bring the work to the 
proper angle with the cutter. In most makes of machines 
it is inconvenient, if not impossible, to swivel the table to a 
greater angle than 45 degrees. For greater angles special 




Fig. 100. Brown & Sharpe Milling Machine arranged in the Usual 
Manner for Cutting Spiral Gears. 



attachments are provided for swiveling the cutter, leaving 
the table in its normal position at right angles to the spindle 
of the machine. Two examples of this are shown in Figs. 
101 and 102. The first case shows a Brown & Sharpe mill- 
ing machine engaged in cutting a spiral gear, using for the 
purpose a vertical milling attachment, which has been set 
to the required helix angle. The change gearing used for 



CUTTING WORMS AND HELICAL GEARS. 



139 



connecting the spiral head with the feed-screw of the table 
can be plainly seen at the left. In Fig. 102 an attachm(^nt 
of another form is shown, built l)y the Cincinnati MilHng 
Machine Company, Cincinnati, Ohio. In this case the 







Fig. lOL Cutting Spiral Gears of Helix Angle too Great to allow the 
Method of Fig. 100; employing the Brown & Sharpe Vertical Mill- 
ing Attachment. 



cutter is adjustable about a vertical axis, being driven from 
the spindle by bevel and spiral gears. It may be set at any 
angle throughout the whole circle, and cuts on top of the 
blank, the table being set in the normal position, the same 
as in Fig. 101. The vertical attachment shifted to a hori- 
zontal position, or a rack-cutting attachment, may also be 



140 



GEAR-CUTTIXG MACHINERY. 



used in milling helical gears to bring the cutter spindle at 
right angles to the main spindle of the machine. By this 
means it is possible to mill gears having a greater lieHx angle 
than 45 degrees without shifting the table more than 



45 degrees. 




Fig. 102. Universal Milling Attachment of the Cincinnati Milling 
Machine Company in use cutting Gears of Large Helix Angle. 

A third attachment, shown in Fig. 103, differs from the 
two previously shown, in the provision of an outboard 
bearing for the cutter spindle, and in the fact that the driv- 
ing is so arranged that the vertical capacity of the machine 



CUTTING WORMS AND HELICAL GEARS. 141 

is not seriously affected by the attachment. In addition, 
it offers the advantage of allowing the cutter to be set 
central with the work before the angular adjustment is 
made. This apparatus is built by the R. K. Le Blond 
Machine Tool Company, Cincinnati, Ohio. 

These various attachments allow the milhng machine to 
work throughout a wide range of angles for heUcal gears 




Fig. 103. Cutting a Spiral of Short Lead on the Plain Milling 
Machine, an Operation Impossible on the Universal Machine with- 
out Special Attachments. 

and worms, the only limitation being one similar to that 
imposed on worm cutting in the lathe, though the limita- 
tion is reversed. For worms or gears of too small lead as 
compared with their diameter, the rotary movement of the 
blank is so great that the comparatively slow-moving feed- 
screw is unable to speed up the spiral head mechanism to 
get the required movement and still furnish power enough 
for feeding the work against the cutter. The operation 



142 



GEAR-CUTTING MACHINERY. 



shown in Fig. 103 is about the Hmit in this direction. For 
greater angles it would be necessary to feed the work man- 
ually by the index crank, driving the feed-screw through 
the change gearing. 

Specialized Forms of Milling Machines for Cutting 
Spirals by the Formed Cutter Method. 

The principle of the universal milling machine for cut- 
ting spiral gears and worms has been applied to the design 
of various special machines for the same purpose. A num- 




FiG. 104. Helical Gear-Cutting Attachment used with the Atlas 
Gear-Cutting Machine shown in Fig. 36. 

ber of these are shown in Figs. 104 to 109. The speciali- 
zation of the machine includes making the spiral and 
indexing mechanisms integral parts of the tool, so that 
they have a much greater capacity for taking heavy cuts 
than is the case where they are merely attachments, as in 
the cases previously shown. 

In the first case shown the spiral cutting mechanism is 
still something in the nature of an attachment, the 
machine being designed for cutting other kinds of gears 
as well. This tool (see Fig. 104) is the universal gear- 
cutting machine made by Nya Aktiebolaget Atlas, Stock- 



CUTTING WORMS AND HELICAL GEARS. 143 

holm, Sweden, already illustrated in Figs. 3G and 77. 
The cutter spindle is mounted in a swiveUng head, which 
may be set at the required angle for the heUx to be cut, 
the angular adjustment thus being identical with that in 
Fig. 103. The cross rail with the cutter is fed down 
through the work, which is rotated by its gearing con- 
nections so as to produce the helix required. In this 
machine the indexing is done by power, being regulated 
by change gears as in the orthodox automatic spur gear 
cutter. There must, then, be some sort of a differential 
gear mechanism combining the indexing movement and 
the rotation of the work for the hehx, both of which must 
be allowed to operate on the work without interfering with 
each other. We are not informed as to the exact nature 
of this mechanism, though it is doubtless similar in prin- 
ciple to that described for the following machine. 

It was stated that the spur gear cutting machine shown 
in Fig. 58 is a modification of a universal gear-cutting 
machine made by J. E. Reinecker, of Chemnitz-Gablenz, 
Germany. In Fig. 105 is shown a side elevation, and in 
Fig. 106 a diagram, of the index worm connections of the 
universal machine referred to, as arranged for cutting heli- 
cal gears by the formed milling process. The machine is 
arranged, like the Becker-Brainard machine (see Fig. 21), 
on the general lines of the miUing machine, excepting that 
the work spindle is at the top of the column and the cutter 
spindle on the knee. 

The cutter, at B, is driven by an internal gear A of 
large diameter (see also Fig. 58) and is mounted on a 
swivel table C, which can be set to the required helix 
angle. The form of cutter slide shown will give any angle 
up to 30 degrees. For greater angles this is replaced with 
a sHde which can be rotated to any angle throughout the 
whole circle. 



144 



GEAR-CUTTING MACHINERY. 



The screw which feeds cutter slide C along the knee is 
driven from cone pulley D, through vertical shaft E and 
its gear connections. Cone pulley D is also connected with 
change gearing F, which is, in turn, connected with the 




Fig. 105. Side View of the Reinecker Universal Gear-Cutting Machine, 
showing the Geared Connections between the Index Worm- Wheel 
and the Feed of the Cutter Slide. 



index worm, so as to rotate index wheel G and the work 
properly, for any desired hehx. The principle of this 
is the same as in the universal milling machine, change 
gears F acting the same as the change gears used to con- 
nect the spiral head with the table feed-screw in Fig. 100. 



CUTTING WORMS AND HELICAL GEARS. 



145 



Now the worm-wheel G is used for indexing, as well as for 
rotating the work for the heUx, in unison with the feecUng 
of cutter sUde C. The way in which these two motions are 
imparted to G without interfering with each other may be 
understood by reference to Fig. 106. Similar parts have 
similar reference letters in this engraving and the pre- 
ceding one. 




Fig. 106. Detail of the Machine in Fig. 105, showing the Differential 
Mechanism by which the Motions for Helical Cutting and for 
Indexing are combined to rotate the Work. 



At H, on the opposite side of the machine from that 
shown in Fig. 105, are mounted the change gears by which 
the indexing is accomplished. These gears drive bevel 
gear /. Index worm K, meshing with index worm-wheel 
G, is mounted on a hollow sleeve, keyed fast to the bevel 
gear L. Shaft M carries a hub with projecting pivots on 
its right-hand end, on which are mounted bevel pinions N. 
Shaft M is driven by worm-wheel 0, connected with the 



146 GEAR-CUTTING MACHINERY. 

feed of the slide cutter through change gears F. Gears J, 
L, and N form a cHfferential mechanism of the well-known 
"jack-in-the-box" type. The action of this mechanism is 
such that if shaft M be at rest, change gears at H may be 
operated for the indexing, transmitting the motion from 
gear J to L through pinions N as idlers, thus revolving 
index worm K. On the other hand, with the indexing 
mechanism still and the cutter slide feeding, the move- 
ment thus imparted to shaft M may be transmitted (by 
the rolling of pinions N on stationary bevel gear J, and 
the consequent rotation of bevel gear L) to worm K, and 
thence to worm-wheel G and the work. It will thus be 
seen that the indexing, and the rotation for the helical 
cutting, can take place independently of each other. But 
more than this, the two motions can be operated together 
without interference. In fact, either of the motions 
imparted to shaft M or gears at H may be stopped or 
reversed independently, and each will have its proper 
influence on the index wheel and the work. 

With this understanding of the differential mechanism, 
the operation of the machine is easily comprehended. 
Change gears H are connected through a one-revolution 
friction trip with the main driving shaft. The cutter, set 
at the proper angle, is fed forward through the work, 
which is rotated by change gears F, shaft M, and worm K, 
at the proper rate to cut the proper hehx. The cutter is 
then dropped down to clear the work (provision for this 
being made in the machine), and returned, ready to begin 
on a new tooth. The indexing mechanism is then tripped 
by hand, and the work is rotated into position for the new 
tooth by change gears at H, gear J, and worm-wheel K. 
This is repeated until the gear is done. 

There were three other spur gear bobbing machines of 
which it was said that they were equipped for cutting the 



CUTTING WORMS AND HELICAL GEARS. 



147 



teeth of spiral gears by the forinecl tool method . These 
were the Ducominun machine in Fig. 59, the Gikle- 
meister machine in Fig. 03, and the Lorenz machine in 
Fig. 70. Fig. 107 shows the Gildemeister machine at 
work on a spiral gear, performing the operation in the 
same way that it is done in the universal milling machine. 
There is no special provision for reheving the cutter on the 
return in these machines, so far as the writer knows. 




Fig. 107. The Gildemeister Machine (see Fig. 63) cutting a Spiral 
Gear by the Formed Tool Process. 



In the Lorenz machine in Fig. 70; the arrangement for 
indexing is different from any that has been described in 
connection with the cutting of spiral gears. At the com- 
pletion of a cut the cutter is returned to the starting 
point ready for the next feecUng movement. The divid- 
ing worm is then disconnected from the feed mechanism 
by which it is controlled when forming the tooth space, 
and is connected with the index mechanism. This latter 



148 GEAR-CUTTING MACHINERY. 

consists of a one-revolution crank, shown at the side of 
the base in the engraving, connected with the dividing 
worm by change gears to give the number of teeth desired. 
After the indexing, the connection is again made with the 
feed mechanism, and the indexing mechanism is released. 
While this intermittent connection with the index mech- 
anism would seem to be dangerous from the standpoint of 
accurate dividing, it is said to w^ork out satisfactorily in 
practice. The index or work-driving worm-w^heel is of 
bronze, driven by a worm of special construction, which 
the builders claim gives a much more durable contact 
than is usually obtained. There is at least one of these 
machines in use in the United States. 

In the machines hitherto shown, power is applied to the 
feed-screw, from which the work is rotated through change 
gearing. This arrangement is best for helices of great 
lead. When it comes to milling helical gears with small 
leads, i.e. worms, it is necessary to use the lathe principle 
and apply the power to rotating the work, the longitudinal 
feed being driven from the work spindle through change 
gearing. We show two examples of machines of this kind 
in Figs. 108 and 109. 

The well-known thread milling machine made by Pratt 
& Whitney, Hartford, Conn., is illustrated in Fig. 108. 
Probably few mechanics have ever thought of this as 
being a gear-cutting machine, but it is here shown engaged 
in the perfectly legitimate work of cutting a worm, so that 
it should be classified with gear-cutting machinery of the 
kind described in this chapter. The machine is so well 
known as to scarcely need description. The cutter spindle 
is mounted in a head which can be swiveled to any angle, 
and the slide which carries it is fed lengthwise along the 
bed, the proper lead being obtained by connecting the 
head-stock spindle and feed-screw by change gearing. 



CUTTliNG WORMS AND HELICAL GEARS. 149 




o 






3 

o 



bC 

C 

c 

c3 



b£ 












CO 

o 






150 



GEAR-CUTTING MACHINERY. 



A second machine of this kind is shown in Fig. 109. It 
is built by J. E. Reinecker, of Chemnitz-Gablenz, Ger- 
many, and is intended especially for milling worms, 
although it is well adapted for small spiral gears also. 
The cutter, driven by worm gearing, is mounted in a 
heavy swivehng head, which is fed along the bed on ways 




Fig. 109. The Reinecker Worm Milling Machine. 



at the rear of the machine. The adjustment for diameter 
is made by moving the work table, with its head and foot 
stocks, away from or toward the cutter. Cone pulleys and 
gearing are provided for varying the rate of feed of the 
cutter head, while the connection between the feed move- 
ment of the cutter and the rotation of the work is governed 
by change gears. On the worm-wheel which drives the work 



CUTTING WORMS AND HELICAL GEARS. 151 

spindle will be seen mounted a change gear mechanism 
which is used for indexing. The indexing is by hand, and 
the whole mechanism is carried around by the spiral move- 
ment, so that a differential mechanism is unnecessary. 

Specialized Formed Cutter Machine for Herring- 
bone Gears. 

There is a speciahzed form of herringbone gear made 
by Andre Citroen & Co., 202 Rue de Faubourg St. Denis, 
Paris. The teeth of these gears, we are informed, are 
shaped by an end cutter like that shown in Fig. 99, guided 
by suitable mechanism to produce the continuous 'Svavy" 
form of herringbone teeth characteristic of these gears. 
This process also has the advantage of not requiring the 
blank to be made in two pieces. The same principle has 
been apphed by the builders to the cutting of herringbone 
bevel gears. 

Other manufacturers make use of the formed end mill, 
to a limited extent, at least. The worms or spiral gears 
which drive the racks of the Sellers drive planers, made 
by at least one of our prominent planer builders, are cut 
by end mills in a specialized milling machine of simple 
design, made especially for this purpose. 

Automatic Machines for Milling Helical Gears 
WITH Formed Cutters. 

A number of full automatic machines have been built 
in an experimental way for milling spiral gears with 
formed cutters. They have usually been modeled after 
the automatic spur gear cutter. Evidently the mechan- 
ism has to be considerably more complicated. The first 
complication involved is due to the fact that the index 
wheel must be under the influence of both the helical and 



152 GEAR-CUTTING MACHINERY. 

the indexing movements, as in the Reinecker machine in 
Figs. 105 and 106. The differential gearing there shown is 
the arrangement generally used to effect the combination 
of these movements in the automatic hehcal gear cutter. 

Another compUcation is introduced by the necessity for 
reUeving the cutter on its return stroke, after finishing the 
forward feed through the blank. Backlash in the rotating 
mechanism between the cutter slide and the work so alters 
the position of the cutter and the work on the return 
stroke that the latter will drag on one side of the groove 
it has just cut, unless it is separated slightly from 
it. This has been done in various ways in the various 
machines built; in some cases by mounting the cutter on 
a supplementary holder which rocks back out of the way 
on the return stroke, and in other cases by withdrawing 
the work by mechanism provided for the purpose. 

These various complications seem to have militated 
against the commercial success of the automatic spiral 
gear cutting machine to such an extent that, so far as we 
know, but one of the various designs built has ever left 
the shop where it was made. The design we refer to is 
that shown in Fig. 110, built by Gould & Eberhardt, of 
Newark, N. J. As will be seen, it is a machine of large 
capacity, built in the form of the horizontal machines for 
cutting spur gears shown in Figs. 32 to 38. The cutter 
spindle is, of course, set in a swiveling head, and is driven 
by worm gearing. Three sets of change gears are used — 
one of them for the indexing mechanism, one for obtain- 
ing the proper lead of the hehx, and one for changing the 
feed. The relieving mechanism operates as follows: As 
the cutter is being rapidly returned to allow the work to 
be indexed for a new cut, the work is withdrawn slightly 
from contact with the cutter by a cam-actuated device 
connected with the indexing mechanism. On the con- 



CUTTING WORMS AND HELICAL GEARS. 153 







:3 
o 
O 

C3 






bL 



:3 

a; 
O 






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a 

o 

13 
<51 






154 



GEAR-CUTTING MACHINERY. 



elusion of the indexing the work is again brought up to 
the cutting position, and the cutter is fed downward for 
a new tooth. 

Molding-Generating Principle for Cutting Helical 
Gears — Planing Operations. 

Passing by the templet, odontographies and describing- 
generating principles, for the reasons mentioned in the 
introduction to this chapter, we come to the molding- 




FiG. 111. The Molding-Generating Principle arranged to employ a 
Cutter having a Helical Shaping Action, cutting Teeth in a Solid 
Blank; compare with Fig. 6. 



generating principle. This is applied to helical gears in 
the same w^ay as to spur gears, with such modifications as 
are necessary to allow for the helical shape of the teeth. 
The counterpart of Fig. G is shown in Fig. 111. The form- 
ing cutter and the blank to be cut are rolled together as in 
Fig. (), while the forming cutter is reciprocated axiall}^ 
In combination with the axial movement, however, the 



cutter has to be given 



a rocking movement about its 



CUTTING WORMS AND HELICAL GEARS. 155 

center line, so that its teeth will follow the path of the 
dotted lines shown, which indicate the helix of the spiral 
gear wdiich the cutter represents. 

This process was contemplated by Mr. Fellows, of the 
Fellows Gear Shaper Company, in the original working 
out of his system of gear cutting. Given suitable cutters, 
the necessary changes in the machine shown in Fig. 79 
would simply be those involved in giving the cutter a 
rotary rocking motion in unison with its reciprocating 
movement, to compel the tooth to follow the line of the 
hehx of the gear which the cutter represents. It is not 
probable that this process will ever come into commcu'cial 
use, as the great number of helix angles required would 
involve too large a stock of cutters. 

The counterpart of Fig. 7, for helical gears, is shown in 
Fig. 112. Here the forming rack has teeth set on the 
same angle as the helix angle desired in the gear being 
formed. The rolling of a plastic blank over this forming 
rack will form in the l^lank helical teeth of the shape 
desired. A top view of the rack is shown, which will 
make this clearer. Instead of the forming rack shown by 
the full lines, we may use one like that shown in the dotted 
lines, whose teeth coincide with those of the first, but 
which moves in a direction at right angles to the direction 
of its teeth. If this dotteil rack is moved at such a rate of 
speed that its teeth ahvays coincide with those of the rack 
shown in full lines, they will evidently both form teeth of 
exactly the same shape in the blank. 

In Fig. 113 we have the dotted rack of the top view of 
Fig. 112, shown engaged in the operation of generating the 
teeth of a gear identical with that in Fig. 112. This view 
has been taken at an angle so as to show the normal view 
of the rack. If the proper relative rates of rotation of the 
work and movement of the rack are maintained in Figs. 112 



156 



GEAR-CUTTIXG MACHINERY. 



and 113, and the normal sections of the racks in each 
case are the same, the gears generated will be the same. 
It is evident in Fig. 113 that the teeth of the rack may be 
replaced by shaper or planer tools T^ and T^, which may 
be used in forming teeth on the blank by rotating the 
gear and moving the tools endwise in the proper ratio 



''^■^^ 

TOP VIEW OF A^C^- - 5* > 

FORMING RACK) IVv \' 



ALTERNATIVE 
FORMING RACK 








Fig. 112. A Rack with Teeth set 
on an Angle, operating by im- 
pression on the Molding-CJener- 
ating Principle, to form Teeth 
in a HeHcal Gear; compare with 
Fig. 7. 



Fig. 113. Shaper Tools represent- 
ing Teeth of Imaginary Rack, 
operating on the Mokling-Gen- 
erating Principle to generate 
Teeth in a Helical Gear; com- 
pare with Fig. 8. 



prescribed by the conditions in Fig. 112. Fig. 113 is thus 
the counterpart of Fig. 8 for helical gearing. Similar 
counterparts may 1)(^ drawn for Figs. 9 and 10, showing 
the mining and grinding processes, but since no practical 
application is made of these they are omitted. 

Fig. 113 is interesting in that it hints at the principle 



CUTTING WORMS AND HELICAL GEARS. 157 

on which the action of the heUcal gearing is based. As 
drawn, it shows very plainly the action of the well-known 
Sellers drive for planers. It will be noted that for a short 
space the rack teeth exactly fill the outline of the gear 
tooth. Contact between the gear and the rack takes place 
on straight lines running diagonally across the plane 
faces of the rack teeth. Much might be WTitten about the 
contact between spiral gears and racks, and the contact of 
spiral gears with each other, that has not been published, 
so far as the writer is aware; but since this subject is not 
germane to the subject of this book it will not be touched 
on here. 

Practical appHcation has been made of the princi[)le 
shown in Fig. 113. The Bilgram spiral gear planing 
machine, involving this principle, is shown in Fig. 114. 
The work is mounted on a spindle carried in a head, which 
swivels about a vertical axis so that it may be set to the 
hehx angle of the gear being cut. The cutting tool, having 
a shape to represent a tooth of the imaginary generating 
rack, is carried by a ram which works in and out, cutting 
on the return stroke. This ram is carried by a head which 
is fed along the bed of the machine. This longitudinal 
feeding of the ram-carrying head is connected with the 
rotary movement of the work spindle by change gearing, 
in the proper ratio for the case in hand, so that the gear 
will roll with the movement of the head just as it would 
if it were acting under the influence of the imaginary rack, 
one of whose teeth is represented by the cutting tool. 
The conditions are thus exactly the same as in Fig. 113. 

Under these conditions, if the machine is set properly, 
the cutting tool will start to work at one side of the blank 
and pass through it, feeding at the end of each successive 
stroke, with the work rolling in such a way as to form a 
tooth space of the proper shape. This action is modified 



158 



GEAR-CUTTING MACHINERY. 



somewhat by the method of indexing adopted, which is 
the same as for the somewhat similar spur gear planing 
machine by the same builder, shown in Fig. 50. The 




Fig. 114. The Bilgram Machine for cutting HeKcal Gears, operating 
on the Principle of Fig. 113. 



arrangement used indexes the work at every stroke, so 
that when the tool has once passed through the work 
the gear is entirely completed, every tooth having been 



CUTTING WORMS AND HELICAL GEARS. 159 

worked on. This indexing movement and the rolhng 
motion required for the generating are superimposed on 
each other by suitable differential mechanism, so that 
neither interferes with the other. 

It may be mentioned incidentally that this machine is 
the only one know^n to the writer in which all the require- 
ments for theoretical accuracy in cutting helical gears 
have been taken care of. There is a minute, though actual^ 
error involved in even the otherwise perfect bobbing pro- 
cess for cutting these gears. 

The Hobbing Modification of the Molding-Gener- 
ating Principle of Cutting Helical Gears. 

Instead of using the shaper or planer tool to take the 
place of the teeth of the imaginary rack shown in Fig. 113, 
we may use a hob, in the same way that it was used in 
Fig. 56 for hobbing spur gears. This condition is shown 
in Fig. 115, which should be compared with Figs. 56 and 
113. The upper or plan view best shows the respective 
angular settings of the work and the hob. The hob is 
set at an angle with the line of movement of the imaginary 
rack, equal to its own helix angle, as for spur gears. The 
gear being cut is set at an angle with this same Hne equal 
to its own hehx angle, so- that in this case (in which both 
gear and hob are right-hand) they are set at an angle to 
each other equal to the difference between the hehx angles. 
If the hob represented by the worm in the diagram is 
revolved in the direction shown, its teeth will have the 
same outline and the same movement as the teeth of an 
imaginaiy rack moving in the direction shown. If the 
work be revolved in the proper ratio with the hob, the 
latter will form the teeth in the former in the same way 
that the imaginaiy rack would, provided it is fed progress- 
ively through the work in the direction of line XX. 



160 



GEAR-CUTTING MACHINERY. 



This necessity for feeding the hob through the work 
introduces an added complexity to the machine in the 
case of spiral gears, beyond that needed for the spur gear 
hobbing machine. To understand this, suppose that in 
Fig. 115 the spindle mechanism is stopped, so that both 
the spindle and work ceased to revolve. To make it 
possible to feed the hob through the work in the direction 
of Hne A^Y without having the teeth of the one strike 



GEAR BEING CUT 



WORM REPRESENTING THE HOB 
WHICH IS CUTTING THE GEAR 




' GEAR BEING CUT 



direction of feeding 
movemenY of HCD 



.IMAGINARY RACK WHICH FORMS 
THE GEAR BY THE MOLDING- 
GENERATING PROCtSS. ITS TEETH 
COINCIDE WITH THOSE OF THE 
HOB, WHEN THE LATTER IS SET 
AS SHOWN. 



Fig. 115. Molding-Generating Method of cutting Spiral Gears, as Ex- 
emplified in the Hobbing Process; compare with Figs. 56 and 113. 



against the other, it will be necessary to revolve either 
the work or the hob. Suppose that the work be connected 
by change gearing with the feed-screw of the cutter slide, 
S3 that it is revolved as the cutter is fed up or down, in 
the same way that the work in Fig. 100 is revolved as the 
table is fed backward and forward. Under these condi- 
tions the cutter may be moved through the work freely, 
the latter revolving to allow the cutter to pass. Not 
only must the work revolve in a definite relation with 
the feeding of the cutter slide, but the work must also 



CUTTLXd WORMS AND HELICAL GEARS. 



161 



revolve in unison with the cutter or hob, as for spur gears. 
It must then be so connected with the cutter and with the 
cutter slide feed-screw that it will be under the influence 
of either or both of them, without any interference of 
the two movements with each other. This connection 
is usually made by a ''jack-in-the-box" or differential 
mechanism, exactly identical in principle with that shown 
in Fig. 106 for combining the indexing and hehcal feeding 



CUTTER SLIDE FEED SCREW 



CUTTER DRIVING SHAFT 




DRIVING SHAFT OF MACHINE 



DIFFERENTIAL, OR JACK-IN-THE-BOX 
GEARING 



WORM FOR REVOLVING WORK TABL? 



mMMm 



CHANGE GEARS FOR LEAD OF SPIRAL 



CHANGE GEARS FOR RATE OF FEED 



Fig. 116. Typical Arrangement of Gearing for Spiral 
Gear-hobbing Machine. 

movements for revolving the work in the Reinecker uni- 
versal machine. In the case of the spiral gear bobbing 
machine we have a helical feeding movement and a cutter 
spindle movement to combine for revolving the work. 

A typical arrangement of the mechanism used for this 
purpose is shown in diagrammatic form in Fig. 116. 
Power is applied to the machine through driving shaft G. 
The bevel gears shown connect this driving shaft with 
vertical shaft //, by means of which the hob is driven. 



162 GEAR-CUTTING MACHINERY. 

Change gears shown connect shaft G with shaft E. Con- 
sidering for the time being that worm-wheel B and the 
attached bevel gear D are stationary, the rotation of E 
and the cross arm A keyed to it will cause bevel gears C 
to roll around on stationary gear D, thereby revolving 
gear L and shaft F to which it is ke3'ed, thus rotating the 
work table. The change gears connecting G and E are 
selected to give the proper ratio of movement between the 
hob or cutter spindle and the work table, to agree with 
the number of threads in the hob and the number of teeth 
in the gear being cut. The cutter sHde feed-screw K is 
connected by change gears with shaft /, which is, in turn, 
connected through the clutch and the bevel gears shown 
with shaft E. The clutch furnishes the means of stopping 
and starting the feed, and the change gears serve to give 
the rate of feed desired. Change gears are also provided 
connecting bevel gear M on feed-screw K with worm L, 
which drives worm-wheel B running loosely on shaft E. 
By this means, supposing for the moment that shaft E 
and its attached cross arm A are stationary, the rotation of 
the feed-screw is communicated through the change gears 
to worm-wheel B and its attached bevel gear D, which, 
driving bevel pinions C on their stationary studs, revolve 
gear L, and with it shaft F and the worm driving the work 
table. In this way, by selecting suitable change gears, 
the work may be revolved to agree with the length of the 
lead of the spiral on which its teeth are formed, so that 
the cutter may be fed up and down through it without 
interfering with the teeth. 

We thus see that the mechanism shown in Fig. 116 may 
be arranged to connect the hob and the work in the proper 
ratio, as for hobbing spur gears, and also for connecting the 
feed-screw and the work in the proper ratio, as for cutting 
spiral gears in the milling machine. But this mechanism 



CUTTING WORMS Ax\D HELICAL GEARS. 163 

not only performs these two functions separately, but it 
will perform them together as well, so that either the feed 
or the cutter-revolving mechanism may be started, stopped, 
or reversed independently of the other movement, and the 
work will still be properly controlled under all conditions. 
The mechanism shown is not that invariably used, but 
it is typical of the arrangement employed in many bobbing 
machines designed for cutting helical gearing. 

HoBBiNG Machines with Cutter Slide on Bed. 

The first bobbing machine for spiral gears we show is that 
in Fig. 117, made by Biernatzki & Co., GO Zschopauerstrasse, 
Chemnitz, Germany. This machine is built on the general 
lines of the orthodox automatic spur gear cutter shown in 
Figs. 22 to 31. The machine is stiffly constructed, the 
column and head being apparently made in one piece. A 
noticeable feature is the rigid construction of the outer 
work support. In a smaller size machine this is mounted 
on the front of the bed, but in the case shown it is supported 
on ways at the rear, behind the cutter slide. A rack and 
pinion movement, operated by hand- wheel, is provided for 
moving it toward or away from the column. This rapid ad- 
justment is very convenient in changing the work. Three 
sets of change gears are used, as shown. Those just behind 
the hand-wheel at the left are set for the lead of the spiral; 
those at the end of the bed are set for the feed of the cutter; 
while the ones at the rear are altered to give the proper 
ratio of movement for the number of teeth in the work 
and the hob, thus closely conforming to the mechanism in 
Fig. 116. One point of difference from its prototype, the 
automatic gear cutter, which may be noted, is made neces- 
sary by the fact that the work is constantly revolving 
instead of being intermittently indexed. The work support 



164 



GEAR-CUTTING MACHINERY. 



clamped to the face of the column in the regular gear 
cutter is usually a simple abutment, adjusted by screw 
and nut to support the work against the thrust of the 




Fig. 117. Biernutzki Gear-hobbino; Machine. 



cutter. In this case, as may be seen, the support carries a 
disk or roller against which the work bears as it revolves. 

Standard Form of Helical Gear-hobbing Machines. 

In the Gould & Eberhardt hobbing machine, shown in 
Fig. 118, the ''horizontal" form of construction has been 
adopted, in which the work is carried by a slide adjusted 
longitudinally on the top of the bed, while the cutter slide 



CUTTING WORMS AND HELICAL GEARS. 165 

is mounted on the face of a vertical column. It thus 
follows the general plan of the machines shown in Figs. 33 
to 88 and 62 to 67. This machine is rigidly constructed, 




Fig. 118. Gear-hobbing Machine made by Gould & Eberhardt, 

Newark, N. J. 



the column and bed being in one piece and special atten- 
tion being mven to the construction of the cutter head and 



"to fe> 



work table to give the stiffness so necessary for accuracy 
and output in a machine of this kind. The outboard 
support for the work is particularly noticeable. It consists 



166 



GEAR-CUTTING MACHINERY. 



of a heavy post, carried by a slide working on the same 
ways as the work table, to which it may be connected to 
form one piece. A rapid traverse for the cutter head is 
provided, so that it is ordinarily unnecessary to operate 
the feed of the cutter slide manually. The cutter head 
may be swung around through an angle of 180 degrees 
above the horizontal. With this arrangement, the driving 




Fig. 119. Gould & Eberhardt Machine cutting Spiral Gears of Large 

Helix Angle. 



gear is always above the center line of the head, so that 
less clearance is required below the work. This means 
that blanks can be held down closer to the table, giving less 
overhang and greater rigidity. In Fig. 119 this machine is 
shown bobbing spiral gears of great helix angle. 

In Fig. 120 is shown a machine built by Holroyd & Co., 
Ltd., of Milnrow, near Rochdale, England. The engraving 
shows a spur gear in the machine having its teeth hobbed, 
but provision is made for bobbing spiral gears as well. 



CUTTING WORMS AND HELICAL GEARS. 167 




O 



'a; 



a; 

O 



O 



IS 



bC 

o 

I 

O 
O 



o 



M 



168 GEAR-CUTTING MACHINERY. 

As may be seen, the cutter spindle is driven by an internal 
gear of large diameter. The engraving shows quite 
plainly the usual method followed of supporting work in 
machines of this type. The work is centralized with the 
table by the arbor which passes through it, but most of the 
support is taken by brackets mounted on the table or 
face-plate and providerl with T-slots in their upper faces 
by which the work is clamped to them. This arrangement 
makes the work practically solid with the face-plate. 

Of the three shafts extending along the front side of the 
bed, the lower one {G in Fig. IK)) is connected with the 
cutter driving mechanism and drives through change and 
differential gearing the upper of the three shafts {F in 
Fig. 110) which is connected with the index worm of the 
work table. A place for change gearing will be seen at 
the base of the column carrying the cutter slide. This 
connects the feed movement of the cutter with the central 
shaft (L in Fig. IKV), which in turn is connected with 
differential gearing in the enclosed casing seen at the right- 
hand end of the bed, in the foreground. 

In this, as well as in previous machines shown, provision 
is made for bobbing worm gearing, the mechanism being 
introduced at the right-hand end of the bed for this purpose. 
Reference will be made to this later. Provision is also 
made for intermittent indexing, so that a formed gear 
cutter can be used. For this purpose the lower shaft in 
Fig. 120 may be driven through a friction slip if desired. 
The lever shown below the differential gear box at the 
right-hand end may be used to release or arrest a disk 
keyed to this shaft, so that it may be allowed to make one 
revolution when desired. The change gears at the end of 
the machine are then set for the number of teeth required. 
Under these conditions it will be seen that it may be used for 
gear cutting by the formed cutter method, being then prac- 



CUTTLNG WORMS A.\D HELICAL GEARS. 169 

tically the same sort of machine as those illustrated in 
Figs. 33 to 38, except that it is not fully automatic. 

In Fig. 121 is shown a gear-hobbing machine built by 




Fig. 12L Newton Machine at Work on a Helical Gear. 

the Newton Machine Tool Works, Inc., Philadelphia, Pa. 
It is shown at work on a spiral gear, which is supported in 
a somewhat different manner from the cases previously 



170 



GEAR-CUTTING MACHINERY. 




o 



o 

oT 

.s 

o 



o 

t 

o 






O 



CUTTLXG WORMS AND HELICAL GEARS. 171 

shown. A special support, in the form of a cast sleeve or 
column, is provided for raising the work high enough 
above the table so that the driving gear of the spindle 
clears the tal)le when the cutter has been fed through the 
work. In cutting spur gears, of course, it is not necessary 
to set the work so far above the table, less clearance being 
required for the spindle driving gear. 

The Pfauter machine, shown in Fig. 122, is sold by 
Schuchardt & Schiitte of New York, Berhn, London, etc. 
The differential mechanism is shown quite plainly in this 
engraving, which represents the No. 4 size. The change 
gearing above the index worm-shaft is for the lead of the 
helix, that below for the feed, while the larger gearing at 
the left end of the machine is for connecting the hob and 
the work in the proper ratio. The cutter spindle of this 
machine is driven by herringbone gears to insure smooth- 
ness of action. This line of machines is made in a great 
range of sizes. The smallest of these has a maximum 
capacity for a blank 6 inches in diameter, while the largest 
will take a gear 104 inches in diameter. Provision is 
made in the larger sizes for intermittent indexing of the 
work table by hand, so that the teeth may be cut by 
formed cutters if desired. The swiveling head is adjusted 
by a worm on the larger sizes. 

HoBBiNG Machines of Special Types. 

The machine shown in Fig. 123, made by the Grant-Lees 
Machine Company, 6901 Quincy Avenue, Cleveland, Ohio, 
cannot be classified structurally with any of the previous 
examples. It is an outgrowth from a bobbing machine 
for worm gears formerly built by its designer, Mr. John 
Grant. The work is mounted on a vertical spindle carried 
by a shde which is adjusted horizontally for the diameter. 



172 



GEAR-CUTTING MACHINERY. 



The feed of the work past the cutter is effected by raising 
the si)indle vertically. The cutter is driven by a com- 
bination of bevel gears which is best shown in Fig. 124, 
and it may be adjusted throughout a full circle. The 




Fig. 123. Gear-hobbing Machine of Special Construction, made by 
Grant-Lees Machine Company, Cleveland, Ohio. 



bevel gear on the hob spindle meshes with a large ring 
bevel gear, which in turn is driven by a bevel pinion on 
the driving shaft. The bevel pinion on the hob shaft occu- 
pies a different j^ortion of the ring bevel gear from that 
occupied by the driving pinion, so it may be adjusted 



CUTTING WORMS AiND HELICAL GEARS. 173 

around the full circle without interference. Provision has 
been made in the mechanism to revolve the work as it is 
fed upward, independently of the movement given by its 
connection with the hob, thus meeting the requirements 
for spiral or helical milling. The machine is shown in 
Fig. 124 completing a hehcal gear. 

A gear-hobbing machine built by George Juengst & Sons, 
Croton Falls, N. Y., is decidedly worthy of study on 




Fig. 124. Grant-Lees Machine bobbing a Helical Gear. 

account of the unique principle involved, although the 
builders have never placed the machine on the market. 
The unique feature is the method adopted for avoiding 
differential gearing. The spur gear bobbing machine does 
not require any connection between the feed-screw and 
the work-revolving mechanism, because the hob can be 
fed back and forth through the work after it has been 
completed, without interference. In the Juengst machine 
the same effect is accomplished by setting the feeding 
movement at the angle of the teeth of the work. As is 
shown in Fig. 125, the work is mounted on the column, 
while the cutter, which may be swiveled to agree with its 



174 



GEAR-CUTTING MACHINERY. 



helix angle, is fed along a slide which may be, in turn, 
swiveled to agree with the helix angle of the work. The 
line of travel of the hob, as shown in Fig. 126, being thus 
set in the same direction as the teeth of the gear, the hob 
can be fed diagonally through the work without interfering 
with the teeth, whether the machine is in motion or not, it 




Fig. 125. Juengst Gear-hobbing Machine, employing a Novel Principle 

for Helical Milling. 

being taken for granted, of course, that the hob and the 
work are properly geared together. Differential gearing is 
thus done away with, being replaced by the swivehng 
adjustment of the cutter slide, which permits the hne of 
travel of the hob to be adjusted to the heUx angle of the 
work. 

This same result has been accomplished in another way 
by a patent granted to an English inventor. With his 



CUTTING WORMS AND HELICAL GEARS. 175 

arrangement the work is niountetl on a face-plate on the 
bed, while the cutter slide feeds up and down the column, 
as usual. The column, however, instead of being solid with 
or bolted to the bed, is mounted on ways so that it may 
be fed horizontally at right angles to the line of adjustment 
of the work table. The feed-screw controlling this adjust- 
ment is connected by change gearing with the vertical feed- 
screw of the cutter slide on the column, so that these two 
movements take place simultaneously in any desired ratio 



\ LINE OF TRAVEL OF HOB IN JUENGST MACHINE 




AXIS OF WORK AND LrNE OF TRAVEL 
OF HOB IN MACHINES OF USUAL 
CONSTRUCTION. 

HOB 






Fig. 126. Method of Feedino; the Hob in the Juengst Machine. 



with each other. By' this means the combined vertical and 
horizontal movements of the cutter slide give a component 
in an angular direction, which may be made to give any 
desired angle of travel, such as that shown, for instance, 
in the line of travel of the hob in the Juengst machine. 
Fig. 120. 

The difficulty with these otherwise attractive plans for 
hobbing helical gears by moving the hob at an angle instead 
of using differential gearing, appears to be that a longer hob 
is required for going in an angular direction across the face 
of the gear than would be necessary in feeding vertically 



176 GEAR-CUTTING MACHINERY. 

downward, as is the case with the usual (Uffcrential mechan- 
ism. The hob would have to be unusually long if it were 
desired to cut a bank of spiral gears in one operation, as is 
being done in Fig. 118. 

There are still other methods possible for taking care of 
the helical movements required besides those already dis- 
cussed. For instance, instead of using differential gearing 
to combine the motion derived from the feed-screw with 
that of the cutter spindle driving shaft, it may be used to 
combine movements derived from the feed-screw with that 
of the index worm shaft and applying the combined motion 
to driving the hob. Furthermore, the differential mechan- 
ism may be discarded entirely, by providing an index worm 
of considerable length and shifting it longitudinally at the 
proper rate in connection with the feeding of the cutter slide. 
This would impose on the work rotation in connection with 
the cutter slide feed without interfering in any way with 
the rotation due to the connection with the cutter or hob. 
Differential gearing would thus be avoided as in the case of 
the Juengst machine. This device would have its limita- 
tions for gears of small lead, as it would require too great a 
length of worm to give the proper amount of rotation to the 
work. 

An example of this latter plan is furnished by the machine 
made by the Pratt & Whitney Company, of Hartford, Conn., 
for cutting the wonderful herringbone gears run at such 
tremendous speed in the De Laval steam turbine. The 
mechanism is shown diagrammatically in Fig. 127. At- 
tached to the cutter head is an angular slide, which may 
be set to any desired angle. A roll is confined in the slot 
in this guide, whose vertical movement thus imparts a 
cross movement to the sliding frame on which the roll is 
mounted. On the frame are mounted the bearings of the 
index w^orm, which is thus shifted endwise with the vertical 



CUTTING WORMS AND HELICAL GEARS. 



177 



movement of the cutter slide; and this endwise shifting 
of the worm, in turn, rotates the index worm-wheel in uni- 
son with the feed of the cutter. By setting the slide 
at a greater or less angle, this rotation of the worm-wheel 
and the work may be adjusted to give very accurately the 
desired lead of the hehx — more accurately, in fact, than 
it can be obtained by change gears, which cannot always 
be selected to give just the movement desired. The rota- 
tion of the work in unison with the hob, it will be seen, is 



Spiral Gear being Cut 




Fig. 127. 



Slidint; Frame Carrying Worm 
Angular Slide and Graduated Circle^ 



Diagram showing Spiral Mechanism in De Laval 
Machine. 



effected by the rotation of the worm, while its rotation in 
conjunction with the feed of the cutter slide is effected by 
the endwise movement of the worm. There is thus no conflict 
between the two movements, which are combined as effec- 
tively as in the differential mechanism shown in Fig. 116. 
This mechanism may be compared with that in Fig. 96. 

Still another method of avoiding the differential gears 
has been employed, which permits cutting spiral gears on a 
spur gear bobbing machine. In Fig. 116, when the three 



178 



GEAR-CUTTING MACHINERY. 



sets of change gears are set for the number of teeth in 
the gear, lead of spiral, and rate of feed, respectively, the 
rotation of the work bears a definite ratio to that of the 
hob. We can then set the change gears between G and E 
to this ratio, disconnect the change gears for the spiral, 
couple E and F together, and get along without the differ- 
ential gears entirely. In other words, the differential is 
avoided by modifying the change gears connecting G and 
E, to agree with the feed and the lead. Whenever either 




Fig. 128. Machine for cutting Solid Herringbone Gears by the 

Wiist Process. 

is changed, this gearing must be changed also. A spur 
gear machine may thus be set to cut any spiral gear 
within the range of the angular setting of the hob spindle, 
if the proper change gears are furnished. This same prin- 
ciple is exempUfied in the worm-wheel cutting machine 
in Figs. 152 and 153. 

It would appear from the drawings furnished the writer 
that the Reinecker universal gear-cutting machine (see Figs. 
105 and 106) could be arranged to hob spiral gears by the 
simple expedient of connecting the indexing change gear 
train positively with the cutter driving mechanism instead 



CUTTING WORMS AND HELICAL GEARS. 179 

of through the friction slip used for the semi-automatic 
indexing. This would give a combination identical in prin- 
ciple with that shown in Fig. IIG. Probably the matter of 
German patent infringements accounts for not using the 
machine for hobbing spiral gears. 

A machine for hchcal gear hobbing, provided with some 
special features, is shown in Fig. 128. This machine is used 
by C. E. Wiist & Co., Seebach, Zurich, Switzerland, for cut- 
ting herringbone gears of a special form, in which it is un- 
necessary to cut the two halves in separate sections, as is 
the usual case. As may be seen in Fig. 129, the cuts are 
staggered so that the teeth on one side run into the spaces 




Fig. 129. A 7-tooth Pinion, formed by the Wiist Process. 

on the other in such a way as to permit cutting them with 
hobs without having the cutting tool on one side interfere 
with the teeth cut on the other side. No detailed informa- 
tion as to the type of differential mechanism used on this 
machine is available, nor is any information given as to 
precautions necessary in the design and setting of the hobs 
to prevent the teeth from running into each other. The 
most interesting thing about the machine is its product; 
the large gear shown in the machine in Fig. 128, and the 
pinion shown in Fig. 129, are examples of two extremes 
in the range of work for which the process is appHcable. 
Besides the machines we have just described, two of the 



180 GEAR-GUTTING MACHINERY. 

hobbing machines illustrated and described under the head- 
ing of spur gear machinery are specially adapted to the cut- 
ting of helical gears. These machines are the Rhcnania 
machine shown in Fig. 65 and the Wallwork machine 
shown in Fig. 67. The only change necessary to adapt 
these machines to cutting spiral gears is the addition of the 
differential gearing and the connection for change gearing 
between the feed-screw and the work table revolving worm. 
Provision is made for this mechanism in the design of the 
machines. Of course all of the hobbing machines we have 
described are adapted for cutting spur gears, and those 
shown in this chapter should be included in the Hst when 
studying spur gear cutting machinery. 

The Field of the Hobbing Process for Cutting 
Helical and Herringbone Gears. 

There are some limitations to the hobbing process of cut- 
ting helical gears. It is not particularly successful in the 
cutting of gears of such small lead and great helix angle that 
they would be classed as worms rather than spiral gears. 
For such cases the rate of rotation which has to be given 
the blank is so great in proportion to the downward feed of 
the cutter by which the rotation is effected (through the 
change and differential gearing) that it is almost impossible 
to drive it, the difficulty being the same in kind, though 
reversed in direction, as that met with in cutting very steep 
pitches in the lathe. By a sUght compUcation of the 
machine, however, mechanism could be introduced to over- 
come this difficulty and make the hobbing machine univer- 
sal for all kinds of gears within its range. 

In the discussion of the hobbing processes for cutting spur 
gears it was stated that its field was not yet definitely deter- 
mined. It may be said, on the whole, that there is no 



CUTTING WORMS AND HELICAL GEARS. 181 

such indefiniteness in regard to the field of the hobbing 
machine for cutting hehcal gears. With a well-constructed 
machine and with hobs of i)roper shape spiral gears can be 
cut more accurately and cheaply by this method than by 
any other known. There are none of the mechanical diffi- 
culties of indexing and relieving to be taken care of as is the 
case in automatic machines working on the formed cutter 
process; and there are none of the uncertainties as to tooth 
shape due to interference met with in cutting a helical 
groove with a formed cutter, as shown in Fig. 99. There 
has been some little difficulty in getting the correct shape 
of teeth by the hobbing process, due to the elasticity of the 
mechanism connecting the hob and the work and to errors 
in the construction of the hob itself. These difficulties, 
however, will surely disappear with further experience and 
investigation. 

Apparently the recent rapid development of the hobbing 
process for cutting spiral gears is the solution of a problem 
which has long seemed somewhat perplexing. The flexi- 
bility of the spiral gear, and the numerous advantages of 
the herringbone or the twisted tooth spur gear for trans- 
mitting great power noiselessly and smoothly at high 
velocities, have long been appreciated, but their extended 
use has waited for the development of some accurate and 
inexpensive method of forming helical teeth. 

This completes the description of machines for forming 
the teeth of worms and helical or herringbone gears. 



CHAPTER VI. 

WORM-WHEEL CUTTING MACHINES. 

To correctly classify and comprehend the various 
methods and machines for cutting the teeth of worm- 
wheels, it is first necessary to clearly define the term 
'Svorm gearing." When we say "worm gearing" in this 
chapter we mean gearing of the type of which a cross- 
section is shown at the right of Fig. 130, in which the act- 
ing face of the wheel is curved to fit the form of the worm 
and in which the whole width of the wheel face is in 
active working contact with the worm. 

The action is best understood by taking a vertical sec- 
tion on the center line A A, and on other lines such as that 
at BB parallel with the center line. Sections on hues 
A A and BB are shown at the right of the cut. With 
worm gearing of standard form the section on line A A 
shows the worm to have the profile of an involute rack, 
while the teeth of the wheel show outlines identical with 
those of the corresponding involute gear of the same pitch 
and number of teeth suited to engage with the rack. In 
other words, the teeth of the gear are such as would be 
formed by the teeth of the worm if the latter acted as a 
rack in a molding-generating operation identical with that 
shown in Fig. 7. A section on line BB shows that the teeth 
of the worm have a distorted outline on planes removed 
from the axial plane. If we consider these distorted teeth 
as the teeth of a rack molding their mating tooth spaces 
in a gear running on the same center as the worm gear 
and at the same speed, it will form, by the process of 

182 



WORM-WHEEL CUTTLNG MACHINES. 



183 



Fig. 7, the distorted wheel teeth shown for the section on 
line BB. In a word, each section of the worm parallel to 
the axial section A A is a rack section which molds in 
the wheel below it the proper teeth to mesh with it in 
accurate conjugate action. The true worm-wheel, it is 
thus seen, must be formed by the molding-generating 
process. 

The same worm as that shown in Fig. 130 may be made 
to engage with a spiral gear of the same number of teeth 




SECTION ON LINE B-B 



Fig. 130. Action of a True Worm-Wheel. 



as the worm-wheel, provided the teeth are of the proper 
pitch and set at an angle to agree with the helix angle of 
the worm. The action of such gearing, however, does not, 
hke that in Fig. 130, take place on all sections A A, BB, 
etc., but is confined to a point at or near the center line 
A A. The contact, in other words, is point contact, and 
not line contact extending clear across the face of the 
wheel. Such a combination, in fact, is not a case of 
worm gearing, but a case of spiral gearing — and a very 
poor case at that. 



184 



GEAR-CUTTING MACHINERY. 



Gashing Worm-wheels by the Formed Cutter Process. 

While the method of forming a true worm-wheel is 
thus seen to be accurately performed only by the molding- 
generating process, the accurate teeth produced by that 
process may be closely approximated in many cases by 
the '^gashing" method, which belongs in the formed 
cutter classification. In this operation, illustrated in Fig. 
131, a milling cutter is used having approximately the 




Fig. 131. Gashiiio; a Worm- Wheel in the MiUino; Machine. 



outhne of a normal section of the teeth of the worm to be 
used. This cutter is of the same diameter as the worm, 
and is set with relation to the axis of the work at the 
hehx angle of the worm, as measured on the pitch line. 
It is centered over the wheel, and fed into the latter to 
the proper depth to form a tooth space; it is then drawn 
out again, the work is indexed to the next tooth space. 



WORM-WHEEL CUTTING MACHINES. 185 

and the cutter again sunk in to depth, the operation being 
repeated until the wheel is completed. In Fig. 131 a uni- 
versal milling machine is being used for this operation. 

With the table set at 90 degrees, the cutter is first 
brought centrally over the work arbor by adjusting the 
saddle on the knee of the milling machine, and then the 
work is brought centrally with the cutter arbor by adjust- 
ing the table by the feed-screw. The work table is next 
swung to the helix angle of the worm which is to be used 
with the wheel. Then the cutting is proceeded with. 

This gashing process gives a tooth very closely approx- 
imating the true tooth form when the diameter of the 
worm is large as compared with the pitch and when the 
worm is single threaded. For multiple-threaded worms of 
smaller diameter in proportion to their pitch the process 
is impracticable. This method is used by at least one 
of the best-known builders of gear-cutting machines in 
forming the teeth in the index worm-wheel. It is used 
under the conditions which give a very close approxima- 
tion to the true form of tooth, and is employed in this 
particular case for the sake of the high degree of accuracy 
obtainable. The index wheel is divided, in cutting, by 
a carefully made and carefully preserved master wheel. 
The step by step gashing process allows the spacings of 
this superior master wheel to be accurately reproduced in 
the index wheel being cut — more accurately than would 
be possible if it were to be reproduced by the hobbing 
operation described later. 

The gashing process is also used for roughing out worm- 
wheels preparatory to hobbing. In a previously gashed 
wheel, as will be explained later, the hobbing operation is 
one of extreme simplicity, not requiring special machines 
or mechanism of any kind. 



186 



GEAR-CUTTING MACHINERY. 



The Molding-Generating or Hobbing Process. 

As explained, the mokling-generating principle is the 
only one for accurately forming the teeth of worm-wheels. 
The principle involved is shown in Fig. 132. The form- 
ing worm (or hob) is connected by gearing with the plastic 
worm-wheel blank to be formed, in the same ratio as 




Fig. 132. Diagram showing the Arrangement of the Mechanism for 
the Hobbing Process for Cutting the Teeth of Worm-Wiieels. 



given by the finished worm gearing. While the blank and 
the forming worm (or hob) are rotated together in this 
ratio, the latter is fed into the blank slowly, its threads 
forming the proper shaped tooth in the wheel. As the 
worm revolves, an axial section would give the appear- 
ance of a rack like that shown in section A A of Fig. 130 
moving continuously and forming suitable gear teeth in 
the wheel below it. Any other section, such as BB in 
Fig. 130, would also act as a distorted rack, forming cor- 



WORM-WHEEL CUTTING MACHINES. 



187 



respondingiy distorted gear teeth in that portion of the 
worm-wheel in the same plane. The process is thus seen, 
as previously explained, to be identical with that in Fig. 7. 
Of the various methods of operation, shaping or planing 
is of course impracticable. MilUng is the method gener- 
ally em})loyed. Grinding or abrasion is used to a limited 
extent, it being sometimes employed in the case of "grind- 
ing in" a worm with a wheel already roughly cut to 
shape. In this operation the worm and wheel are run 
together in place under considerable pressure, the teeth of 
the gear being liberally supphed with sand, ground glass, or 



i^*%4' 





Fig. 133. Side and End VievA's of a Worm Gear Hob. 



rouge, which acts as an abrasive and forms the teeth of 
the gear and worm to fit each other. 

In the commonly employed milling operation the pro- 
cess is that known as '^hobbing/' and the milling cutter 
or tool used is a "hob," of which an example is shown in 
Fig. 133. The hob (barring modifications required for 
reUef or clearance, and allowance for regrinding) is practi- 
cally a replica of the worm which is to be used, but with 
grooves cut in it so as to form teeth. This hob is rotated 
in the proper ratio with the work, exactly as shown in 
Fig. 132, and fed slowly down into it, cutting out the 
tooth spaces in the wheel as it does so. Wlien it has 
reached the proper depth, the teeth are all formed to the 
proper shape. 



188 



GEAR-CUTTING MACHINERY. 



HoBBiNG Worm-wheels in the Milling Machine. 

The simplest method of rotating the hob and the work 
in the proper ratio with each other is that in which the 
work is first gaslied, as shown in Fig. 131, and then fin- 
ished with the hob in such a way as to be driven by the 
latter, the work and the hob thus furnishing their own 

The same wheel which is 



driving mechanism. 



being 




Fig. 134. Hobbing a previously Gashed Worm-Wheel on Dead Centers 

in the Milling Machine. 



gashed in Fig. 131 is shown having its teeth finished to 
the proper shape with the hob in Fig. 134, the hob driv- 
ing the work as described. The latter is mounted so as 
to revolve freely on dead centers. This is the simplest 
method of making correct worm-wheel teeth. It does not 
require special appHances of any kind, being done in an 
ordinary milling machine with a gashing cutter and a hob. 
In cases where it is desired to hob worm-wheels directly 



WORM-WHEEL CUTTING MACHINES. 



189 



from the solid without prcHminary gashing, it is necessary 
to provide some special device for rotating the hob and 
the work in unison as in Fig. 132. Such a case is shown 
in Fig. 135, which illustrates the Le Blond attachment of 
Fig. 57 arranged for hobbing worm-wheels. The connec- 
tion between the cutter spindle and the work is the same 
as for spur gears, but the work is fed verticahy up into the 




KiG 135. Hobbing Attachment for the LeBlond Milling Machine, 
Cutting a Large Worm- Wheel. 



hob instead of being fed past it by the regular table 
movement. The driving connections are more plainly 
shown here than in Fig. 57. 

Another attachment for the same purpose, but differ- 
ently arranged, is shown in Fig. 130. This is built by the 
Wanderer Fahrradwerke, Schonau, bei Chemnitz, Germany. 
This attachment is self-contained, and carries a vertical 
work spindle, driven by a worm and worm-wheel, which 



190 



GEAR-CUTTING MACHLNERY. 



are in turn connected by change gearing with a spiral 
gear driven from the shaft. The hob is fed to depth in 
the work by the operation of the regular feed-screw. The 
analogy between this mechanism and that shown in Fig. 
132 will be readily traced. 

In Fig. 137 is shown a hobbing attachment applied to 
another form of miller, in this case a horizontal spindle 




Fig. 136„ The Wanderer Positively-driven Attachment for Hobbing 
Worm-Wheels in the Milhng Machine. 



machine of the planer type made by the Newton Machine 
Tool Works, Philadelphia, Pa. The attachment consists 
primarily, as in the previous case, of a base provided with 
bearings for a vertical spindle, which is revolved by a 
worm-wheel enclosed within the base. The worm is con- 
nected by change gearing with a splined shaft driven 
through a train of gearing from the spindle. The machine 
is set to the diameter of the work, and the hob is fed to 



WORM-WHEEL CUTTING MACHINES. 



191 



depth by the operation of the regular longitudinal feed- 
screw. A special feeding mechanism is provided, oper- 




FiG. 137. Positive Hobbing Attachment used in the Newton Milhng 

Machine. 

ated from the attachment instead of from the regular feed 
cones. 

Hobbing Worm-wheels in Machines Designed for 

Cutting Other Forms of Gearing. 
With shght changes, the orthodox spur gear cutting 
machine can be adapted to hobbing worm-wheels. An 
example of such an adaptation is shown in Fig. 138, the 



192 



GEAR-CUTTL\G MACHINERY. 



machine adapted in this case being an automatic gear cutter 
made by the Newark Gear Cutting Machine Co., of Newark, 
N. J. The indexing mechanism is operated from the same 
sphned shaft by which the spindle is driven, so that, to 
obtain the proper ratio of movement between the hob 




Fig. 13S. Orthodox Gear-Cutting Machine arranged for Robbing Worm- 
' Wheels, with Ratchet Feed operated from Index Wheel. 



and the work, it is only necessary to connect the index 
gearing positively with the driving shaft, instead of using 
the intermittent indexing m.otion ordinarily employed. 
With the index gearing thus permanently connected with 
the spindle driving mechanism, proper change gears may 



WORM-WHEEL CUTTING MACHINES. 193 

be selected to give the required ratio of movement 
between the worm-wheel to be cut (which is, of course, 
mounted on the work arbor) and the hob, carried on the 
cutter spindle in place of the regular spur gear cutter. 
Another provision that has to be made is that for feeding 
the cutter into the wheel as the work progresses. This is 
effected in this particular case by lugs on the arms of the 
index wheel, which, rotating continuously, act on a link 
mechanism which operates an adjustable ratchet motion 
for the vertical feed shaft. This ratchet motion may be 
varied to give any rate of feed desireil. By this means 
the work is fed down into the cutter as the operation pro- 
gresses. 

In Fig. 139 is shown a gear-cutting machine made by 
Gould & Eberhardt, Newark, N. J., arranged for bobbing 
worm-wheels. In this case, also, the hob and the work 
are connected by means of the splined driving shaft and 
the index gearing, so that they revolve in unison and in 
the proper ratio. It will be seen that the work in the 
machine is so heavy as to make it advisable to support the 
outer end of the work arbor by means of the outboard 
bearing regularly provided for that purpose. To permit 
the downward feeding of the wheel, necessary to sink the 
cutter in to depth, the adjusting screw of this outboard 
bearing and the elevating screw of the work spindle head 
are geared together, so that they work in unison. The 
feed movement is applied to these two screws in such a 
way as to gradually lower the work into the cutter as the 
two revolve together. 

All of the various gear-hobbing machines we have 
shown in Figs. 58 to 72 and 117 to 126 are adapted to the 
bobbing of worm gears without requiring special attach- 
ments of any kind. The only requirement in addition to 
the mechanism needed for bobbing spur gears is the pro- 



194 



GEAR-CUTTING MACHINERY, 




Fig. 139. Gould & Eberhardt Gear-Cutting Machine arranged for 

Hobbing Worm-Wheels. 



vision of a feed mechanism for sinking the cutter in to 
depth. The work saddles or tables of most if not all these 
machines are provided with this feed movement. The 
gearing for revolving the work and the hob in proper 



WORM-WHEEL CUTTING MACHINES. 



195 



ratio with each other is of course embodied in the design 
of this type of machine. In Fig. 140 is shown one of 
these hobbing machines (the Grant-Lees machine of Fig. 
123) engaged in hobbing a worm gear. 

In addition to the machines we will describe later in 
which, though the hobbing process may be used, different 
movements are involved than in the cases we have been con- 




FiG, 140. Worm-Wheel being finished in Grant-Lees Gear-hobbing 
Machine (see Figs. 123 and 124). 



sidering, special hobbing machines have been built from time 
to time, identical in their action with the various machines 
shown in Figs. 135 to 140. Most of these machines have 
been specially built to suit the requirements of the user, 
without conforming to any settled type or design ; very few 
of them have been built as a commercial product to be 
placed on the market. The Grant-Lees machine, however, 
was originally a worm-gear machine pure and simple, being 
afterward adapted to hobbing spur and spiral gears. 



196 GEAR-CUTTING MACHINERY. 

The Fly-tool and Taper Hob Methods of Cutting 
Worm-wheel Teeth. 

By providing a suitable driving and feeding mechanism 
it is possible to use a simple fly-cutter for forming the teeth 
of worm-wheels in place of the expensive hob used in the 
operations previously described. The movements required 
for this method will be understood from a study of Fig. 141. 
Here is shown in dotted lines a worm meshing with a worm- 
wheel, a portion only of whose periphery is seen. As pre- 
viously described in referring to Fig. 130, such a worm, 
properly located with reference to a plastic blank and 
rotating with it in the proper ratio, will form accurate teeth 
in the latter by the molding-generating process. As we 
have also previously described, gashing this worm makes 
of it a cutter by means of which the same form may be given 
to a blank of solid metal. The teeth of such a gashed hob 
coincide with the outlines of the thread of the worm. 

In Fig. 141, in full lines, is shown a cutter bar with a blade 
T^ of the same outline as the thread of the worm and the 
tooth of the corresponding hob. In order to permit this 
single cutting tool to perform the function of the worm as 
it molds a plastic substance, or of the hob as it cuts its 
shape in metal, it must be fed helically as the bar and work 
revolve, following the outlines of the imaginary worm from 
one end to the other as the cutting progresses. Beginning 
at the left, for instance, the blade may be fed helically in 
the line of the thread, passing through positions T^ and T.^, 
until the feed finally runs out at the extreme right. 

The methods of giving this progressive helical change of 
position to the fly-cutter are various. It would be possible, 
for instance, to so connect the feed-screw by which the cut- 
ter bar is advanced with the rotating mechanism for the bar, 
through differential and change gearing, that a rotating 



WORM-WHEEL CUTTING MACHINES. 



197 



movement due to the axial feeding of the latter would be 
added to or imposed upon the rotation due to its connection 
with the work, just as, in Fig. UG, the rotation due to the 
downward feed of the cutter slide is combined with that due 
to the connection with the cutter spindle for rotating the 
work. If the proper change gears were selected so that, 
with the spindle- and work-driving mechanisms stationary, 
the feeding forward of the cutter bar would rotate the latter 
at the proper rate to give the lead of the work, the blade 

, IMAGINARY V/ORM, FORMING TEETH IN THE WHEEL BY THE MOLDING-GENERATING PROCESS. 
CUTTER BAR WITH BLADE, Tl , WHICH PROGRESSIVELY FOLLOWS THE 1 
THREAD OF THE WORM, AND SO CUTS THE TEETH OF THE WHEEL J 






/~i\ r^' r~^ i^pTh n^ 




ft / // // I 



^^7? / . ^i /f/TT '/ /'//w ^7 ifV'// / 






I 'i 

u 




Fig. 141. Diagram showing the Principle of the Fly-Tool Method of 
cutting the Teeth of Worm-Wheels. 



would evidently follow the path of the thread of the imagi- 
nary worm, as shown at T^ and T^ in Fig. 141. Owing to 
the action of the differential mechanism, it would still 
follow the thread of the imaginary worm, even if the latter, 
with the spindle- and work-driving mechanism, were in 
motion. 

Another method consists in combining in the work, also 
by differential gearing, a rotation due to the revolving of the 
cutter with a rotation due to the axial feed of the cutter bar. 



198 GEAR-CUTTING MACHINERY. 

That this produces the same effect as the previous arrange- 
ment will also be understood from Fig. 141. 

First, let the rotation of the cutter be arrested. If the 
cutter bar with a w^orm mounted on it, such as shown by 
the dotted lines, be now fed axially in the direction of the 
arrow, the positive connections between the feed and the 
work spindle through the change gearing and the differen- 
tial gearing will cause the work to rotate uniformly with it. 
If the feed is arrested after a time, and the bar is started 
revolving, the imaginary worm mounted on it will still be 
kept in proper mesh with the work, owing to the change 
gear connections between the cutter bar and the work spin- 
dle acting through the differential gearing. As we have 
previously explained, the office of the differential gearing 
is to combine in the work the rotation due to the feeding 
and that due to the rotation of the worm, in such a way 
that they can take place simultaneously as well as sep- 
arately; so that it will be seen that if the connections are 
properly made the worm may be fed endwise and revolved 
at the same time, always keeping in perfect step with the 
work. 

Now, the imaginary worm and the fly-tool are both firmly 
fixed to the cutter bar, so that the fiy-tool must always 
follow the movements of the imaginary worm. Being set 
to coincide with the outUnes of the worm thread at the 
start, it must always coincide with those outlines, and since 
the worm is never out of step with the work, the fly-tool also 
will never be. It will thus be seen that it will always fol- 
low the helical path of the dotted lines in Fig. 119, in mov- 
ing, for instance, from T^ to T^. Revolving in the position 
T3, T^, T2, etc., the work, as shown in the dotted lines of 
T^, will always be in proper relation with the fly-tool, as 
it is with the imaginary worm. 

With this arrangement, if the change gearing connecting 



WORM-WHEEL CUTTING MACHINES. 



199 



the driving mechanism of the cutter bar and the work were 
disconnected while the bar was fed through from left to 
right, the rotary motion given by the connection of the 
feed of the bar with the work" would shape one tooth. If, 
on the other hand, the gearing connecting the feed of the 
bar with the rotation of the work were disconnected while 
the connections between the drive of the bar and the work 
were in operation, the cutter would partially shape each 
tooth of the work. By combining the two movements in 





Fig. 142. The Taper Hob, adapted to the Fly Cutter Machine. 



the difTerential gearing the cutter perfectly forms all the 
teeth. 

Another form of cutting tool, the taper hob, shown in 
Fig. 142, may be used in machines adapted for cutting 
teeth by the fly-tool method. This tool is fed through the 
worm-wheel along the spiral path of the imaginary gener- 
ating worm, as in the previous case. It is fed small end 
first, and sinks into the work deeper and deeper until the 
full diameter at the rear has been reached. Wlien this has 
passed through the work the gear is finished. The taper 



200 



GEAR-CUTTING MACHINERY. 



hob and the fly-tool may be used indiscriminately in the 
machines shown in Figs. 144 to 153 inclusive. 

The original machine for using the taper hob, built by 
Mr. Reinecker, employed a different form of combining or 
differential movement from that just described. It is 




INDEX WORM TRAVERSING SCREW 



Fig. 143. 



Diagram of Original Form of Mechanism for Generating 
Worm- Wheels with Taper Hob. 



shown diagrammatically in Fig. 143. In this case the 
tapered hob is connected by change gearing with the worm 
driving the indexing wheel, as before. The worm, however, 
is mounted on a sUde, allowing it a considerable range of 
axial movement. This axial movement is controlled by a 
screw and nut, as shown. This screw is connected by 
change gearing with the screw by which the taper hob is 



WORM-WHEEL CUTTING MACHINES. 201 

fed. It will thus be seen that the feeding of the hob rotates 
the work by shifting the index worm lengthwise, while the 
rotating of the hob rotates the work through the rotation 
of the index worm and worm gear. The two movements 
are independent of each other, but are combined with the 
same effect as produced by the "jack-in-the-box" differen- 
tial gearing previously described. With this arrangement 
the ratio of table movement and lengthwise worm move- 
ment should l)e proportioned in the ratio of the pitch 
diameters of the worm-wheel being cut and the index worm- 
wheel. The reason for abandoning this construction was 
doubtless its limited range of movement, which, though 
enough for the bobbing of worm-wheels, was not enough 
(when applied to the universal gear-cutting machine, Figs. 
105 and 106) for cutting spiral pinions of great helix angle. 

Machines and Attachments for Cutting Worm-wheels 
BY the Fly-tool or Taper Hob Method. 

The device shown in Fig. 144 is used in the shops of the 
Garvin Machine Company, New York City, for bobbing 
worm-wheel ^segments for automobile steering gears. The 
fact that the wheel to be cut is segmental makes it necessary 
to have some form of positively driven apparatus, and the 
taper hob principle has been adopted, probably for con- 
venience in using the power cross feed with which the mill- 
ing machine is provided. The mechanism is identical with 
that in Fig. 143, but is considerably simpler, since the 
attachment is made for bobbing one size of gear only. The 
index worm is of the same diameter and pitch as the worm 
with which the finished segment is to mesh, so it is geared 
to run at the same speed as the hob. The index wheel 
is also a duplicate, in its essentials, of the work. The taper 
hob is fed into the work by feeding the table and saddle 
outward on the knee by the automatic cross feed. 



202 



GEAR-CUTTING MACHINERY. 



The first regular machine we show employing the pro- 
gressive fly-tool principle is the product of the Nya Aktie- 
bolaget Atlas, of Stockholm, Sweden. This is the same 
machine that we have previously described, and illustrated 
in Figs. 36, 77, and 104; in Figs. 145 and 146 it is shown 
set up for cutting worm-wheels. The machine is driven 
from cone pulley A. Shaft B, to which this pulley is keyed. 




Fig. 144. A Positive Robbing Attachment, employing a Taper Hob- 



is connected by the bevel gearing shown with vertical 
splined shaft C, from which, through change gears D and 
driving gear E, the fly-cutter arbor F is driven. Gear- 
ing in case G connects shaft C with horizontal driving shaft 
H, which rotates the worm for revolving the work table 
and the work. Change gears D thus furnish the means for 
rotating the work and the hob in the proper ratio with each 
other. 

Pulley J is connected inside the frame to the feed shaft 



WORM-WHEEL CUTTING MACHINES. 



203 



K, seen in the end view. K is connected through change 
gears L and M with shaft A^, which also leads to casing G. 
Change gears M are not altered for cutting worm gearing, 
being emijloyed for indexing in the case of spiral and spur 
gears. Change gears L, however, are set to the lead of the 




Fig. 145. The Atlas Gear-Cutting Machine, also shown in Fig. 36, 
arranged for cutting the Teeth of Worm- Wheels by the Fly-Tool 
Process. Note Quadruple Fly-Tool on the Floor at the Base of 
the Machine. 



worm. Shaft K, besides being thus connected to shaft A^, 
drives, through suitable shafts and gearing, feed screw 0, 
by means of which is traversed on the cross rail the sHde 
on which the fly-cutter arbor is carried, this arbor F being 
driven by a spline in the hub of gear-wheel E. Casing G 
contains differential gearing which combines the move- 



204 



GEAR-CUTTING MACHINERY. 




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WOIiM-WHEEL CUTTING MACHINES. 205 

ments of .hafte C ami .V in sliaft H. It will thu.s bo sec-n 

that by setting change gear« D the work will be g v™ a 

otafon to correspond with the ratio of the number of 

hreacs n, the wonn and the number of teeth in the gear 

while by setting change gea« L properly the work wifl be 

rotated m unison with the axial feeding of the cutter ba 




Fig. 147. Newark Gear-Cutting Machine Company, Fly Tool W 

Wheel-Cutting Machine, with Sam^. of Work ™' 

as in movino^ T to T in Fio- i fi +i n^^' 

conditions. " "' ^^^' ^'^^^ ^"'"8 '^' "^^c^^aiy 

Aside from the ingenuity of tlie mechanical movements 
«ius de.scr.bed, this well-known machine i.s carefully 
planned throughout, being of pleasing design an^Ih S 
construction, considering the variety o worki nt^; 'd 



206 GEAR-CUTTING MACHINERY. 

to perform. This work includes, as we have before men- 
tioned, the cutting of hehcal, internal, spur, and worm 
gears. 

Another machine of the same class, built by the Newark 
Gear Cutting Machine Company, 6(3 Union St., Newark, N. J., 
is shown in Figs. 147 to 149. In this tool the work table 
is stationary as to its position on the bed, while the column 
carrying the cutter slide is adjusted in and out to suit the 
diameter of the work, thus reversing the conditions that 
obtain with the Atlas machine in Fig. 145. Another change 
in the construction is in the provision for the axial feeding 
of the cutter bar. In the case of this machine, instead of 
supporting the cutter on a slide which is fed along the cross 
rail, as in Fig. 145, the supports for the bar are stationary, 
the latter being fed through them by a sUding head (P in 
Figs. 148 and 149) at the outer end of the cross shde. By 
this means the cutter bar is brought much closer to the 
face of the column, and one of the sliding joints between it 
and the column is eliminated. Both of these features tend 
toward rigidity and consequent increase in output. 

The mechanism will be easily understood from a study 
of the diagrams in Figs. 148 and 149. Driving pulley A 
is connected by gears B (which are changed to give the 
desired spindle speeds) with shaft D, which, by means of 
bevel gears C, in turn drives vertical splined shaft W, by 
means of which connection is made with the worm and 
worm-wheel E which drives the cutter bar. Shaft D is 
continued along the bed to change gears F, which are 
changed to give the proper ratio between the rotation of 
the cutter and of the work. These gears drive one of the 
members of the differential gearing X. 

Feed cone J is connected by gearing K with shaft Q. 
The latter, through two sets of worm gearing and vertical 
shaft L, drives horizontal shaft M on the cross rail. From 



WORM-WHEEL CUTTING MACHINES. 



207 



here, through gears A^, the movement is led to feed-screw 
by which head P is traversed to feed the cutter bar 
axially. Q is also connected by change gears R and the 




worm gearing shown with differential gearing Z; gears R 
are selected to agree with the pitch diameter of the work. 
In difterential gearing X, motions from shafts D and Q are 
combined to rotate the work table and the work in the same 



208 



GEAR-CUTTING MACHINERY. 



way as in the Atlas machine and as required in Fig. 141. 
For small blanks the spindle is rotated through spur gear- 
For heavy work, however, a driving pinion is 



ing at H 




He 1, 11 I ' 






fcJC 



o 
o 



fcJD 






too 
o 



> 






fo 



directly connected with teeth on the inner rim of the work 
table, so that a ver>^ powerful drive is obtained. 

This machine can also be arranged to use the ordinary 
cylindrical hob, in which case the feed of head P is thrown 
out, and the column U is fed inward on the bed by means 



WORM-WHEEL CUTTING MACHINES. 



209 



of screw F, so that the hob enters the blank in the same 
manner as for the machines in Figs. 134 to 140. 
The machine shown in Fig. 150, built by John Holroyd 




o 

'o 
o 
H 



ri 

O 



H 



O 

H 



o 






& Co., Ltd., Milnrow, near Rochdale, England, is similar 
in general design to that illustrated in Fig. 147, in that 
the work spindle is vertical and stationary as to loca- 
tion on the bed, while the cutter slide is carried by a 



210 



GEAR-CUTTING MACHINERY. 



column horizontally adjustable for the diameter of the 
work. The machine is of unusual size and capacity. It 
will hob wheels from 12 inches to 72 inches in diameter. 
The main bearing of the work spindle is 8 inches in diam- 




FiG. 151. Machine for Generating Worm-Wheels with a Taper Hob; 
built by J. E. Reinecker, Chemnitz, Germany. 



eter by 16 inches long. The approximate weight of the 
whole apparatus is ten tons. This same firm builds a 
machine of similar design for smaller work, in which, how- 
ever, the work spindle is horizontally adjustable instead of 
the cutter slide column. 



WORM-WHEEL CUTTING MACHINES. 211 

In Fig. 151 is shown a gear-hobbing machine built by 
J. E. Reinecker, of Chcmnitz-Gablenz, Germany. This 
machine has the movements required for performing the 
work of the Atlas ami Eberhardt machines, since it com- 
bines in the rotation of the work a movement due to the 
longitudinal feed of the cutter spindle and a movement 
due to the rotation of the cutter spindle. It is ordinarily 
used, however, with a hob instead of a fly-cutter. This 
hob is tapered as shown. The machine is practically 
identical with the universal gear cutter by the same 
maker, previously shown in Figs. 105 and 100, it being 
adapted, as there shown, to cutting worms by the same 
process. The differential mechanism used is the same as 
in Fig. 100, the axial feed of the cutter spindle being applied 
to shaft M, while the rotative movement of the cutter 
spindle is connected with shaft H, the two being com- 
bined in gears J, L, and A^ to rotate the indexing wh(*el G. 

In Figs. 152 and 153 are shown half-tone and line 
engravings of a fly-tool gear-hobbing machine built by 
Henry Wallwork, Ltd., Redbank, Manchester, England. 
The work is carried by the face-plate and vertical spindle 
A, while the fly-tool B is mounted in the cutter spindle C. 
This latter is supported in slide D, which is adjustable on 
the top of the bed for the diameter of the work, and is fed 
axially by screw E. The fly-tool starts in at one side of 
the work and feeds axially through it, the work and tool 
revolving together, as in previous cases. A peculiarity of 
this machine, however, is that no differential mechanism 
of any kind is employed. The way in which this is 
avoided may be explained thus : 

Suppose that in the Eberhardt machine in Fig. 148 the 
fly-cutter be engaged in h()l)bing a worm-whet^ of 100 
teeth to mesh with a single-threaded worm. If, ihvn, 
the fly-cutter makes 100 revolutions per minute, the worm- 



212 



GEAR-CUTTING MACHINERY. 



wheel will make one revolution per minute. If now the 
cutter spindle be fed longitudinally with a certain definite 
feed, the differential mechanism will modify the rate of 
rotation of the worm, making it slightly more or slightly 
less than one revolution per minute, depending on the rate 
of the feed and its direction as compared with the direc- 
tion of rotation of the work. We may say, then, that if 




Fig. 152. The Wallwork Machine, which cuts the Teeth of Worm- 
Wheels with a Fly-Tool without using Differential Gearing. 



the cutter revolves at a certain number of revolutions per 
minute and feeds at a certain fraction of an inch per min- 
ute, the work will rotate at a certain number or fraction 
of a number of revolutions per minute. Where the gear- 
ing required with the Eberhardt machine would give a 
ratio of 100 to 1 between the hob and the work, as modi- 
fied by the feed this ratio might be 100.0073 to 1, for 



WORM-WHEEL CUTTING MACHINES. 



213 



instance. It will thus be seen that since these conditions 
remain constant until the work is completed, the differ- 
ential mechanism may be dispensed with entirely if we 
select the change gears connecting the hob and the work 
to agree with the new rate of turning of the work as modi- 
fied by the feeding of the hob. 

This is what is done in the Wallwork machine. The 
driving shaft F is connected with the driving cone G either 
directly or through back gears, as may be required. This 




Fig. 153. Vertical Section through Wallwork Worm-WIieel 
Generatino; Machine. 



shaft, through worm-wheel H and change gears shown in 
Fig. 152, drives feed-screw E. It also has keyed to it 
worm J, meshing with the indexing worm-wheel by which 
the work on the vertical spindle A is rotated. At the 
extreme right in Fig. 153 this driving shaft is connected 
with cutter spindle C by change gears /v, mounted on a 
sector which is provided with a worm-wheel adjustment at 
L for setting it, owing to its great weight. It will thus 
be seen that the feed, the work, and the cutter bar are 
all connected by positive gearing. For setting up the 



214 GEAR-CUTTING MACHINERY. 

machine, suitable change gears for connecting screw E 
with the driving-shaft mechanism are used to give the 
desired rate of feed. Then change gears K are selected to 
give the proper ratio between the work spindle A and 
cutter spindle C, as determined by the ratio between the 
number of threads in the worm and the number of teeth 
in the worm-wheel, modified (as explained) by the rate of 
feed. The change gears are set from calculated tables. 
This arrangement would seem to possess both advan- 
tages and disadvantages as compared with the difTerential 
scheme. It results in a much simpler mechanism, but it 
makes it impossible to change the feed without changing, 
as well, the gearing connecting the work spindle and the 
hob. The same principle is used for spiral gear hobbing, 
see pages 177 and 178. 

Cutting Wheels for Multiple-threaded Worms by 
THE Fly-tool Process. 

The method of cutting multiple-threaded worms was not 
described in (Uscussing the principle of the fly-tool process. 
At the base of the machine in Fig. 145 is shown a form of 
tool which may be used for cutting wheels to match with 
multiple- threaded worms. In this case, in which a quad- 
ruple thread has to be provided for, a cutter head is pro- 
vided in which four blades are carried, spaced equidistant. 
The feeding through of these four blades simultaneously 
finishes the worm-wheel complete in one operation. An 
alternative method would be to index the cutter bar with 
relation to its driving gear, giving it three positions for a 
triple-threaded worm, four for quadruple threads, etc. 
This could be done by a notched index plate and lock- 
ing bolt, or by unmeshing the gearing from engagement 
at some point in the driving train and shifting it the 



WORM-WHEEL CUTTING MACHINES. 215 

; required number of teeth before reengagin^^ it. No special 
provision has to be made, of course, for multiple- threaded 
taper hobs. 

The Various Methods Compared. 

Each of the various methods of cutting worm-wheel 
teeth which we have described has its field of usefulness. 
Gashing, as we have seen, is appUcable either to cheap, 
rough-and-ready work on the one hand or, on the other hand, 
to the cutting of worm-wheels which are not required to 
transmit a great amount of power but in which the highest 
degree of accuracy is reciuired. The process of hobbing 
previously gashed > blanks requires the least degree of 
specialization in the machinery used, the ordinary milling 
machine having all the movements and adjustments 
required. This process is perhaps the one followed in 
most shops in making worm gearing of small size. The 
arrangement (such as shown in Figs. 132 to 140) in which 
the work and the hob are positively geared together 
so that previous gashing is not required, is quicker than 
the last mentioned method, but requires special machines 
or attachments. The fly-tool method requires a still 
more elaborate machine, but is the least expensive of all 
in the matter of cutting tools. A large hob is an exceed- 
ingly costly appUance, and raises the cost of production 
to an alarming degree, particularly when but one worm- 
wheel has to be cut. The use of a simple fly-cutter, 
which may be grovmd accurately to size after hardening 
so that all inaccuracies are avoided, is thus the cheapest 
as well as the most accurate means of cutting a large 
worm-wheel. Where many large wheels of the same size 
are to be cut, the taper hob method would seem to be a 
most satisfactory one. A high degree of accuracy could 
be maintained, as the full-size teeth at the back end of 



216 GEAR-CUTTING MACHINERY. 

the hob do not come into play until the finishing cut is 
reached, so that they tend to preserve their shape indefi- 
nitely. Another item that tends to accuracy in this 
method of hobbing is the fact that the distance between 
the work arbor and the cutter spindle is fixed at exactly 
the distance between the axis of the worm and the worm- 
wheel in the finished gearing. This is a refinement of 
greater importance than is usually realized, and one that 
is not always looked out for in hobbing operations in 
which the cutter spindle is fed in toward the work. Hob- 
bing by this method is, of course, more rapid than by the 
fly-tool process employed on the same machines, though 
the latter is not a tedious operation by any means, as a 
solidly supported and powerfully driven tool can be given 
a heavy feed, taking off chips of respectable thickness. 

The methods followed in cutting the other member of 
this form of gearing, the worm, have already been de- 
scribed in connection with machines for cutting helical 
and herringbone gears. 

The Manufacture of Hindley Worm Gearing. 

An old form of gearing which has come into extensive 
use of late years in elevator service and other applications 
in which considerable power has to be transmitted, is 
shown in Fig. 154. This is commonly known as ''Hindley 
worm gearing," though it is not worm gearing at all, 
being entirely different in its action. It should properly 
be classed as ''globoid" gearing, a term which, so far as 
the writer knows, was first employed by Prof. Reuleaux. 
The characteristic feature of its action is the fact that con- 
tact takes place on or near the axial plane of the worm, as 
shown in the engraving. Unlike other forms of gearing, 
neither member of this pair has a pitch line or a pitch 



WORM-WHEEL CUTTING MACHINES. 



217 



diameter. The form of gearing is an old one, but it has 
only recently come into practical use. 

It is often stated that this style of gearing gives surface 
contact, but this statement can scarcely be true. The 
impression doubtless arose from a consideration of sec- 
tions on the two planes shown in Fig. 154, in which it 




Fig. 154. The Form of Globoid Gearing generally known as "Hindley 

Worm Gearing." 

may be seen that the wheel is curved to fit the worm, and 
the worm is curved to fit the wheel, thus giving the appear- 
ance of intimate contact over the whole face of the tooth. 
It is probable that the surfaces more nearly match than m 
ordinary worm gearing, giving an approximation to sur- 
face contact. 



218 



GEAR-CUTTING MACHINERY. 



Any positively operated worm-wheel bobbing attach- 
ment or machine, such as shown in Figs. 135 to 140, may 
be used. The manufacture begins with the cutting of the 
worm, which is effected as shown in Fig. 155. The blank 
is mounted on the spindle of the machine ordinarily occu- 
pied by the hob, while a large-diameter disk provided with 
cutting tools clamped to its face is mounted in place to 



TOOLS-REPRESENTING TEETH OF WHEEL 




Fig. 155. Method of Cutting Hindley Worm with Rotary Cutter 
having Teeth corresponding with those of the Wheel. 



represent the worm-wheel. The cutting tools mounted on 
this disk each represent a tooth of the wheel, being of 
the same shape and cutting on the same diameter. They 
are clamped to the face of the disk in such a way that the 
whole arrangement represents accurately a central section 
of the worm-wheel, of which (in this particular case) only 
every other tooth is used. This cutter and the worm to 
be cut are geared together^ and slowly fed toward each 



WORM-WHEEL CUTTING MACHINES. 



219 



^other as when bobbing worm-wheels. The teeth, cutting 
deeper and deeper into the blank, finally form it into the 
characteristic '^hour-glass" shape of the Hindley worm. 

In cutting the wheel, the process is reversed, as shown 
in Fig. 156. A hob cut in the same way as the worm in 
Fig. 155, but with its teeth relieved, is fed into the wheel 
blank and cuts the teeth in a way exactly identical with 




Fig. 156. Cutting the Teeth of the Hindley Wheel with a Hob corre- 
sponding with the Worm. 



the method followed in hobbing worm-wheels, the only 
difference in the process being the difference in the shape 
of the hob and in the shape of the teeth produced. 

The foregoing description applies to what may be 
called the ''classical" form of Hindley gearing. As made 
for practical purposes, the operations just described are 
used for roughing only. A second cut is taken over the 
worm by the same tool as in Fig. 155, but with the 



220 GEAR-CUTTING MACHINERY. 

blades set to a larger diameter. This trims off the inner 
faces of the worm teeth. Then the worm and the wheel 
are run together with sand or ground glass. This is the 
true finishing operation, which gives a bearing consider- 
ably different from that of the theoretical gear, and one 
difficult of analysis. The process of cutting Hindley 
worms and wheels has never been rationaUzed, so far as 
the writer knows, and is dependent on previous experi- 
ence and good judgment for its success. 

This completes the consideration of machines and pro- 
cesses for cutting the teeth of worm gears. 



CHAPTER VII. 

MACHINES FOR FORMING THE TEETH OF BEVEL GEARS. 

In studying methods and machines for cutting the 
teeth of bevel gears we come to the most fascinating 
branch of the whole subject which we have been consider- 
ing. So great is the number and variety of these machines 
that it will be impossible to do more than give the bare 
outhnes of the ingenious mechanisms which have been 
devised for this work. Almost any of those here described, 
operating on the templet or the molding-generating 
principles, would require a dozen pages and as many 
illustrations to explain the details of its construction. 
We can, however, in the comparatively short descriptions 
here given, get an understanding of the principles of 
operation of each of them. This will best be clone by 
analyzing the various principles of action and methods of 
operation applicable to the cutting of bevel gear teeth, 
as was done for spur gears in Chapter I, following the 
same classification there given, but making the necessary 
changes in the mechanisms shown in Figs. 1 to 10 to fit 
them for the work of cutting bevel gears instead of spur 
gears. 

The changes required in the spur gear cutting devices to 
adapt them for cutting bevel gears, made necessary by 
the difference in the nature of the two forms of gearing, 
are explained in Figs. 157, 158, and 159. The action of a 
pair of mating spur gears may be seen and studied on 
the plane perpendicular to their axes. To be understood 
correctly, the action of bevel gearing, on the other hand, 

221 



222 



GEAR-CUTTING MACHINERY. 



must be observed on a spherical surface. In Fig. 157 
are shown three bevel gears with axes OA, OB, and OC. 
The bevel gear on axis OA is of the form known as the 
"crown gear." It is practically a rack bent in a circle 
about center 0. Pinion OB and gear OC are familiar 
types of bevel gears. In Fig. 158 are shown the pitch 
surfaces of the gears in the preceding figure. It will be 
seen in Fig. 157 that the pitch lines of the gear on the 
axis OC, for instance, converge at the center 0. These 
pitch lines represent a conical pitch surface which is shown 



A 








Figs. 157, 158, 159. Illustrating the Spherical Basis of the Bevel 
Gear, and Tredgokl's Approximation for Developing the Outhnes 
of the Teeth on a Plane Surface. 



cut out from a sphere on axis OC in Fig. 158. In a similar 
way the cone about axis OB represents the pitch surface 
of the pinion, while the plane face of the hemisphere at the 
left of Fig. 158 is the pitch surface of the crown gear of the 
preceding figure. If we wish to draw accurate represen- 
tations of the teeth of the bevel gears in Fig. 157, in order 
to study their action in the same way that we can when 
drawing the teeth of spur gears on the plane surface of the 
drawing-board, we would have to draw them on surfaces 
of the sphere from which the pitch cones in Fig. 158 are 
cut. The pitch circles, etc., of the various gears would 
be struck from centers located at the points where the 



FORMING THE TEETH OF BEVEL GEARS. 223 

Various axes OA, OB, and OC break through the surface 
of the sphere. Except for the different surfaces on which 
the drawing would be done, the procedure would be 
identical with that for spur gears. It should be noted 
that straight Hues on spherical surfaces are represented 
by great circles, that is to say, by the intersection with 
the surface of planes passing through the center of the 
sphere. 

Owing to the impracticabihty of the sphere as a drawing- 
board, an approximate process, known as ''Tred gold's," is 
usually followed for laying out the teeth of bevel gears 
approximately. This is shown in Fig. 159 appHed to the 
same case as in the two preceding figures. The conical 
pitch surfaces vanishing at the center are identical with 
those in Fig. 158, as is also the plain circular face of the 
crown gear. For the bevel gear and pinion, however, the 
teeth are supposed to be drawn and the action studied on 
surfaces of cones complementary to the pitch cones, that 
is, on the cones with apexes at c and b. The surface 
of these cones can be developed on a flat piece of paper, as 
partially shown for that on axis OC, in which case the 
pitch Hne becomes the arc xy. Teeth drawn on this 
pitch line, as for a spur gear, may be laid out on the conical 
surface and used as the outlines of bevel gear teeth. The 
difference in the shape of tooth obtained under the same 
system by the two methods shown in Figs. 158 and 159 
is so slight as to be negligible, except, perhaps, in gears 
having very few teeth. Whatever the method pursued 
for laying out or studying the action, all the elements of 
which the teeth are formed consist of straight lines which 
meet at the center of the pitch cones; consequently the 
teeth grow small toward the inner end, vanishing at the 
center if they are carried that far. 



224 



GEAR-CUTTING MACHINERY. 



Five Principles of Action. 

All of the five principles of action on which spur gear 
teeth may be formed (the formed tool, the templet, the 
odontographic, the describing-generating, and the molding- 
generating principles) may be also appHed to the cutting 
of bevel gears, though the describing-generating principle 
has never been so used, as far as the author's knowledge 
goes, so we will not give any time to its consideration. 




Fig. 160. Shaping the Teeth of a Bevel Gear by the 
Formed Cutter Process. 

The Formed Tool Principle: The use of this principle is 
illustrated in Fig. 160, where we have a bevel gear blank 
set in position to have the tooth spaces cut by a formed 
milling cutter. This method, though perhaps the common- 
est employed of all, is in its nature an approximate one 
only, it being impossible by it to form the tooth correctly. 
The reason for this may be seen in Fig. 160, where it is 
evident that the right-hand side of the cutter is reproducing 
its own unchanging outhne along the whole length of the 
base of the tooth at the right. This form should not be 
unchanging, for, as previously explained, the teeth and the 



FORMING THE TEETH OF BEVEL GEARS. 225 

spaces between them grow smaller toward the apex of the 
pitch cone, where they finally vanish; so it is evident that 
the outline of a tooth at the small end should be the same 
as that at the large end, but on a smaller scale — not a 
portion of the exact outUne at the large end, as produced 
by the formed tool process and as shown in the figure. 
To make this error as small as possible, it is customary to 
use a cutter which gives the proper shape at the large end, 
and set the blank so that the tooth is cut to the proper 
pitch line thickness at the small end. This leaves the 
top of the tooth at the small end too thick, an error which 
is often remedied by filing. Of course, the principle is the 
same with the formed planer or shaper tool as with 
the formed milling cutter, and the errors involved in 
the process are also identical. It is evident that but one 
side of the tooth space can be cut at a time, so that at 
least two cuts around will have to be taken. 

The Templet Principle: This principle is illustrated in 
Fig. 161, in skeleton form only. A former is used which 
has the same outline as would the tooth of the gear being 
cut if the latter were extended as far from the apex of the 
pitch cone as the position in which the former is placed. 
The tool is carried by a slide which reciprocates it back 
and forth along the length of the tooth in a line of direction 
(OX, OY, etc.) which passes through the apex of the 
pitch cone. This sHde may be swiveled in any direction 
and in any plane about this apex, and its outer end is 
supported by the roller on the former. With this arrange- 
ment, in the case shown, as the slide is swiveled inward 
about the apex, the roll runs up on the former, raising the 
slide and the tool so as to reproduce on the proper scale 
the outhne of the former on the tooth being cut. Since 
the movement of the tool is always toward the apex of the 
pitch cone, the elements of the tooth vanish at this point. 



226 



GEAR-CUTTING MACHINERY. 



and the outlines are similar at all sections of the tooth, 
though with a gradually decreasing scale as the apex 
is approached — all as required for correct bevel gearing. 
The arrangement thus shown diagrammatically is modi- 
fied in various ways in different machines, but the move- 
ment imparted to the tool in relation to the work is the 



SECTION OF gear) 
BEING CUT I 



LINE OF travel) 
OF TOOL ) 



APEX OF 
PITCH CONE 




(ROLLER WHICH 
'\gUIDES THE TOOL SLIDE 

Fig. 161 Diagram illustrating the Templet Principle for Forming the 

Teeth of Bevel Gears. 

same in all cases where the templet principle is employed, 
no matter what the connection between the former and the 
tool may be. 

The OdontograpMc Principle: As explained for spur 
gears in Fig. 3, it is often possible to approximate the 
exact curves required for the teeth of gears by mechanisms 
which make use of circular arcs or other easily generated 
curves. In Fig. 162 is shown in diagrammatic form an 
arrangement for obtaining, by means of link work, a close 
approximation to the exact form of an involute outline, 
such as might be produced by the templet in Fig. 161, 
for instance. This true involute outline may be very 
closely approximated by a circle drawn on the surface of a 
sphere. To give this required circular movement to the 
point of the tool, the sHde on which the tool reciprocates 
may be constrained by a link as shown, pivoted at the 
base to the frame of the machine, and at the upper end 
to the slide. The axes of these pivots should pass through 



FORMING THE TEETH OF BEVEL GEARS 227 

the apex of the pitch cone, as required by the spherical 
nature of the bevel gear. This link work (which is thus of 
the "conical" type), if properly proportioned and located. 



SECTION OF GEAR BEING CUT, 



LINE OF TRAVEL"! 
OF TOOL j 




'CONICAL LINK WHICH 
GUIDES THE TOOL SLIDE 



Fig. 162. Diagram illustrating the Odontographic Principle for 
forming the Teeth of Bevel Gears. 

will guide the tool slide and the tool point in very nearly 
the same way as a properly constructed templet, used as 

shown in Fig. IGl. 

The Molding-Generating Principle: The counterpart ot 




Fig. 163. The Impresson Operation, applied to forming the Teeth of 
a Bevel Gear by the Molding-Generating Process. 

the spur gear process shown in Fig. 5 is illustrated for the 
bevel gears in Fig. 163. Here a correctly formed gear is 



228 GEAR-CUTTING MACHINERY. 

being rotated in the proper position and in the proper ratio 
with a plastic blank. This operation, as in the case of the 
spur gear, forms teeth in the plastic blank which are 
properly shaped to mesh with the forming gear or with 
any other gear of the same series. Fig. 6 has, obviously, 
no possible counterpart in the cutting of bevel gears. 

Four Methods of Operation. 

By Impression: The same four methods of operation 
as for spur gears may be apphed to the molding-generating 
principle, and quite generally to the other principles as 
well. Instead of using for illustration a rack as the gener- 
ating member, we will have to use its bevel gear counter- 
part, the crown gear shown in Fig. 157. The impression 
method would simply consist of roUing the crown gear on 
axis OA and the pinion blank on axis OB together, when, 
if the latter were formed of a plastic material, the teeth 
of the crown gear would produce in its smaller mate cor- 
responding tooth spaces and teeth of the proper shape. 

By Shaping or Planing: There is but one form of tooth 
to which the planing operation of mokling-generating is 
adapted. This is the form in which the crown gear has 
teeth with plane sides, which may be cut with a straight- 
sided tool. If the drawing of an involute rack (with 
straight-sided teeth) were wrapped around the periphery 
of the disk in Fig. 159, and the tooth outlines thus deter- 
mined used for teeth vanishing at 0, the resulting crown 
gear would be very nearly of this type. In Fig. 104 such 
a crown gear is shown combined with a simple mechanism 
for making use of the planing or shaping operation in 
the molding-generating process. The gear being cut is 
keyed on a loosely revolving spindle, to which is also keyed 
a master gear, formed on the same pitch cone and having, 
in this case, the same number of teeth. This spindle is 



FORMING THE TEETH OF BEVEL GEARS. 229 



so set in relation to the axis about which the crown gear 
revolves, that the master gear and the crown gear mesh 
together properly, the crown gear being of the required 
pitch and having the proper number and shape of teeth 
for this action. If now the crown gear be rocked about its 
axis, the master gear will also rock with it, carrying the 
gear being cut. 

The blade is set, as shown in the view at the right, so 
that its cutting edge coincides with the plane of one of the 
teeth of the crown gear, and it is held in a slide which 



MASTER GEAR 




STATIONARY FRAME 
CROWN GEAR. 




^BLADE REPRESENTING 

•{side of crown gear 

( TOOTH 
RECIPROCATING TOOL SLIDE 



Fig. 164. Simple Mechanism illustrating the Shaping or Planing 
Operation, applied to the Molding-Generating Principle of forming 
the Teeth of Bevel Gears. 

guides it in such a way that it moves in this plane, so that 
its point follows the line OX, radiating from the apex 
of the pitch cones. The tool will evidently represent 
the side of the tooth of an imaginary crown gear, which is 
adapted to mesh properly with any bevel gear (such as 
that shown being cut) keyed to the master gear and having 
the same pitch cone shape and number of teeth. 

If, with the mechanism so arranged, the crown gear be 
rotated so as to start the cut at one side of a tooth of the 
work (which should be first roughly cut to size) the con- 
tinued rotation of the crown gear will roll the master gear 



230 GEAR-CUTTING MACHINERY. 

in such a way that the reciprocating blade (representing tlie 
side of an imaginary crown tooth meshing with the work) 
will shape the side of the tooth being cut to the proper form, 
by the molding-generating process, on the same principle as 
shown in Fig. 8. 

This arrangement, of course, is not a practical working 
machine as shown, since there is no provision for making 
it universal for cutting bevel gears of other pitch cone angles 
and numbers of teeth, or for indexing the work with relation 
to the master gear to cut the remaining teeth of the work 
shown in place. Arranged as shown, however, the machine 
will cut any gear within its range, of the same pitch cone 
angle and number of teeth as the master gear. To cut a 
different number of teeth it would only be necessary to 
alter angle XOY, as required, setting the slide at a greater 
angle for fewer and larger teeth, or at a less angle for more 
and smaller teeth. 

This principle will be found applied in this and in modified 
forms in machines we will describe later. One of the modi- 
fications which will be seen is equivalent to making the 
crown gear in Fig. 164 stationary, and swinging the frame 
around it about axis OA, thus rolling the master gear and 
the work in the same relation to the tool as when the 
frame is stationary and the crown gear is revolved, in the 
way we have just described. Still another possible modi- 
fication would consist in holding the master gear and work 
still, while the frame is swung about axis OB. In this 
case the crown gear would roll on the master gear, rocking 
the tool slide in such a way as to give the required move- 
ment. It is not possible to form a tooth space complete 
with a single tool, as shown for spur gears, at T^ in Fig. 8, 
without cutting the tooth space too deep at the outside end. 
A separate blade has to be used for each side of the space 
or of the tooth. 



FORMING THE TEETH OF BEVEL GEARS. 231 



Bu Milling, and by Grinding or Abrasion: Milling cutters 
or grinding wheels may be used to represent the shape of the 
tooth, as they represent the rack tooth for spur gears in 
Figs. 9 and 10. In Fig. 165 is shown diagrammatically an 
arrangement by which two cutters or grinding wheels may 
be made to represent the two sides of a tooth in such a way 
that by them a tooth space may be finished complete in the 
gear to be cut in a mechanism similar to that in Fig. 164, 




IMAGINARY CROWN GEAR, FORMING 
THE BLANK BY THE MOLDING- 
GENERATING PROCESS. 

DISKS REPRESENTING ACTING 
FACES OF GRINDING WHEELS OR 
MILLING cutters; THEY COIN- 
CIDE WITH THE PLANE FACES 
OF A TOOTH OF THE CROWN GEAR. 



Fig. 165. Diagram suggesting the Arrangement of Milling Cutters or 
Grinding Whqels for forming the Teeth of Bevel Gears by the 
Molding-Generating Process. 

but without requiring the reciprocating movement. The 
same difficulty arises as in spur gears, of the center of the 
tooth being cut in deeper than the ends, owing to the circular 
form of the cutter. This, however, makes no change in 
the action of the finished gear. 

The variety of apphcations for these various principles 
and methods of operation is fully as great in bevel gears 
as in spur gears, and the machines in which they are 
incorporated apply these principles and methods in an 
even more ingenious fashion. 



232 



GEAR-CUTTING MACHINERY. 



Machines using Formed Milling Cutters for Shaping 
THE Teeth of Bevel Gears. 

One of the most commonly used machines employing the 
formed tool process is the ordinary milling machine. An 
example of the use of the Cincinnati miller for this purpose 
is shown in Fig. IGG. The work is held on an arbor carried 




Fig. 166. Cutting Bevel Gear Teeth on a Milling Machine l^y the 

Formed Cutter Method. 



by the spindle of the universal head, by which the blank is 
indexed for the required number of teeth. The head is 
set to the proper angle to make the bottom of the tooth 
space horizontal. As explained in the paragraph describing 
Fig. 160, it is ])ossi!)le to cut but one side of a tooth 
space at a time, if teeth of even approximate accuracy are 
desired. For this reason, and to obtain as nearly a correct 
form of tooth as possible, the side of the tooth to be cut is 
moved away from the cutter horizontally and then the 



FORMLNG THE TEETH OF BE\'EL GEARS. 233 

work spindle is revolved to bring it up to it again, the 
amount of "set-over" and "rolling" being adjusted by 
judgment and by "cut-and-try," to give the best results. 

The automatic attachment built by Ludwig Loewe & Co., 
and shown in Fig. 15, is also adapted to the cutting of bevel 
gears in the milling machine, which it renders automatic, 
doing the work under the same conditions as in the regular 
machine shown in Figs. 108 to 171. 

The dividing head of the milUng machine may also be 
used on the shaper table, for indexing the work and setting 
it to the proper angle, when cutting the teeth with a shaper 
tool having a l)lade formed to the proper outline. The 
necessary set-over and rolling movements required to 
reproduce an approximation to the correct form are 
exactly identical with those necessary for the milling 
machine. The shaping process may be used for odd jobs 
where no formed cutter is available. 

In Fig. 107 is shown a special machine which is identical 
in principle with the milling machine when used as shown 
in Fig. 166. Being built, however, especially for the work 
of cutting bevel gears, it is of simpler construction and less 
expensive. The bed of the machine carries sHding ways 
at the right, on which is mounted a knee on the face of 
which the cutter spindle is vertically adjustable. The latter 
is driven, through the twisted and bevel gearing shown, from 
a wide-faced pulley of large diameter. The knee is not 
mounted directly on the slide but is carried by an inter- 
mediate saddle along which it is adjustable in and out 
for the depth of cut. The feed is provided with an auto- 
matic stop, but is returned by hand. The work is mounted 
on a spindle set in a head, which may be clamped at the 
proper cutting angle on the base by which it is supported. 
This base may be adjusted toward or away from the cutter 
as well as parallel with the movement of the latter, to 



234: 



GEAR-CUTTING MACHINERY. 



approximately the position required. The work is indexed 
by a notched plate operated by hand. The index locking 
pin is itself carried by an arm which may be swung about 




Fig. 167. A Special Milling Machine for Cutting Bevel Gear Teeth. 



the axis of the work by a worm and worm-wheel adjustment 
to give the required roUing movement, independently of 
the indexing, for correcting the shape of the teeth. What 
corresponds to the cross movement given the blank in 
the milling machine is effected here by the vertical adjust- 



FORMING THE TEETH OF BEVEL GEARS. 235 

ment of the cutter spindle on the face of the knee. Pro- 
vision is made for making both of these adjustments 
positively and quickly. This machine is built by Etablisse- 
ments Marcel Lejeune, 93 Rue D'Angouleme, Paris. 




Fig. 168. Brown & Sharpe Automatic Spur and Bevel Gear Cutter, as 
set up for Cutting Bevel Gear Teeth. 

Another favorite way of using the fonried cutter princi- 
ple for cutting the teeth of gears employs a modification of 
the orthodox automatic gear-cutting machine, such as pre- 
viously shown in Figs. 22 to 31 inclusive. When this is 
done, one side of the tooth can be finished clear around 
without attention from the operator, the cutter slide feed- 



236 



GEAR-CUTTING MACHINERY. 



ing up, returning, and the work indexing, as for spur gears. 
The cutter has to be set out of center with the blank and 
the latter rotated, to approximate the correct form, as with 
the machines previously described. After going around 




Fig. 169. Cutting a Bevel Gear on the Gould & Eberhardt Automatic 
Machine of the Orthodox Type. 

one side of the tooth, this adjustment has to be reversed to 
complete the other side, so that two operations are neces- 
sary. Fig. 168 shows the Brown & Sharpe gear-cutting 
machine as provided with the angular cutter slide adjust- 



FORMING THE TEETH OF BEVEL GEARS. 237 

iXient for bevel gears, and Fig. 169 shows a Gould & Eber- 
hardt machine arranged for the same work. Probably the 
greater proportion of the bevel gears made are cut on ma- 
chines of this kind rather than in other ways. For slow 




Fig. 170. An Attachment to the Flather Automatic Spur Gear 
Cutter for the cutting of Bevel Gears. 

running gears, the approximation, especially if the teeth 
are afterward filed, may be made close enough to be correct 
for all practical purposes. For large, high-speed gears to 
transmit power, one of the planing processes to be described 
later should be used. 



288 



GEAR-CUTTING MACHINERY. 



In Fig. 170 is shown still another method of adapting the 
orthodox gear-cutting machine to the work of cutting bevel 
gears. The machine shown in this case is that built by the 
E. J. Flather Manufacturing Company, of Nashua, N. H., 
and illustrated in Fig. 25. The attachment consists of a 




Fig. 171. The Whiton Automatic Gear-Cutter. 

supplementary work spindle connected with the main work 
spindle by bevel gearing in such a way that it may be 
adjusted to any angle, thus making it unnecessary to com- 
pHcate the cutter slide and feeding mechanism. The at- 
tachment is suitable for work of small diameter, and may 
be applied to machines not originally designed for cutting 
bevel gears. 



FORMING THE TEETH OF BEVEL GEARS. 



239 



An American machine of the same structural type as 
tWsLn.nFigs.33ana3.,builtbyD.E.Wh.onM^^^^^^^^ 

ComDany New London, Conn., is shown m Fig. 171 Unlike 
S,e two English machines it is arranged for cutting beve 
gea.^ as welt as spur gears, the cutter slide being mounted 
on an adiustable sector which may be set to the cutting 




Fig. 172. Rear View of a " Universal " Automatic Gear-Cuttirxg Machine. 

angle of the bevel-gear which is to be milled. It is fully 
automatic, and one of the features of its -*— '^^^ 
provision tor making the starting of each movement depend 
ent on the successful completion of the previous one. T^^a 
is to say, the mechanism is so arranged that the re^e.se 
eed is 1 eked until the forward feed is co-plcted, and 
the indexing is locked until the reverse has been properly 



240 GEAR-CUTTING MACHINERY. 

made. There are no frictional devices, and but one stop 
adjustment — that for length of stroke, which also releases 
the indexing device. 

An example of the machine with the L-shaped bed, such 
as shown in Fig. 42, but arranged for cutting bevel gears, 
is shown in Fig. 172. The ways which carry the cutter 
slide are mounted on a housing which is adjusted about a 
vertical axis to agree with the angle of the gear being cut. 
The machine is fully automatic, and is driven by a single 
pulley. It will cut spur gears and face gears, as well as 
bevel gears; and since the ways of the cutter slide have a 
second angular adjustment about a horizontal axis, teeth 
which are not in the same plane with the axis of the gear 
may be cut in spur gear blanks. Such gears may be satis- 
factorily used as worm-wheels for rough work, if the angle 
of the cut is made equal to the helix angle of the worm 
thread. The machine is built by the Newark Gear Cutting 
Machine Company, Newark, N. J. 

The automatic idea has been carried further than in any 
of the cases previously illustrated, in a machine developed 
a few years ago by the Brown & Sharpe Manufacturing Com- 
pany, of Providence, R. L, for cutting bevel gears for chain- 
less bicycles. These gears were to be made in enormous 
quantities, so that the time lost in the side adjustment and 
the roUing of the work to bring the blank and cutter into 
position for cutting the other side of the teeth, after one 
side had been completed, consumed sufficient time to make 
the elimination of the operation profitable. The machine 
shown in Fig. 173 was therefore devised to first feed the 
cutter through, with the cutter and work set properly for 
finishing one side of the tooth; when the cutter had passed 
through the work, the slide on which it was mounted was 
shifted to a different angular location, so that when it was 
fed backward to its starting position, the return cut operated 



FORMING THE TEETH OF BEVEL GEARS. 241 

on the opposite side of the tooth space, under conditions 
which finished it to the desired form. This change in angu- 
lar position of the tool slide was so adjusted as to be equiva- 
lent to the rolling of the blank and the sidewise movement 







Fig. 173. A Special Bevel Gear-Cutting Machine in which provision is 
made for shifting the Line of Travel of the Cutter; Both Sides of 
the Teeth are finished automatically. 



of the cutter or work, required in cutting bevel gears in the 
milling machine or automatic gear cutter. 

This machine indexes the work by a notched plate, stops 
the feed when the last tooth has been cut, and is in other 
ways adapted to the rapid manufacturing of gears in large 



242 GEAR-CUTTING MACHINERY. 

quantities. The gears are afterwards finished by a mold- 
ing-generating process to be described later (see Figs. 194 
and 195); in which the inaccuracies inherent in the formed 
tool principle are smoothed out. Of course, its usefulness 
is not limited to the bicycle field for which it was first 
designed. 

Attachments for Forming the Teeth of Bevel 
Gears by the Templet Principle. 

The templet principle has found a much wider commer- 
cial application for cutting bevel gears than for cutting 
spur gears. This is due to the fact that the formed tool 
method, as we have seen, is not suited to producing theo- 
retically accurate teeth in the bevel type of gear as it does 
in the case of the spur, since it does not give to the teeth an 
outline at the small end similar to that at the large end. 
Since the templet process is the least compHcated way of 
forming a taper tooth similar in outHne from one end to 
the other (in other words, one whose elements vanish at the 
apex of the pitch cone), a number of very successful com- 
mercial machines have been built involving this principle. 
The first cases we will consider, however, are not complete 
machines, but attachments to the shaper. 

In Fig. 174 is shown an attachment built by the Act.- 
Ges. fiir Schmirgel- u. Maschinen-Fabrikation, Bocken- 
heim-Frankfurt am Main. This is mounted on the shaper 
table so that the angularly adjustable head which carries 
the work spindle overhangs the side. The w^ork spindle 
is indexed with worm and worm-wheel and index plate as 
in the case of the milling machine dividing head. This 
indexing mechanism is attached to a quill which is jour- 
naled in the work spindle head. It has adjustably mounted 
on its outer end a bar B, to which a holder is attached for 
supporting the templet D. An outer arm C, supported 



FORMING THE TEETH OF BEVEL GEARS. 243 

from the frame of the attachment by a bar G, carries a roll 
which is adapted to engage with the edges of templet D. 
The blank, in feeding, is swung up into the tool about 
center A. This swinging movement is operated by a worm 
and worm-wheel sector controlled by a ratchet feed. As the 
work is thus gradually fed up into the tool, the action of 




Fig. 174. A German Shaper Attachment for forming the Teeth of 
Bevel Gears on the Templet Principle. 



the roll on the templet will rock bar B and the quill and 
index motion attached to it, thus swinging the work in such 
a way as to reproduce the outhne of the templet on the 
outside of the tooth. The action is thus identical in its 
effects with that in Fig. 162, though the templet is used to 
control the work instead of controlling the tool. 

The attachment shown clamped to the shaper table in 
Fig. 175 is the invention of Mr. Fred Mill, 704 Prytania Avenue, 



244 



GEAR-CUTTING MACHINERY. 



Hamilton, Ohio. The design of the attachment will best be 
understood from the line elevations in Figs. 176 and 177. 
The work spindle is carried in a head B, which is swung on 
horizontal trunnions A in housing C. This housing is held 
by semicircular gibs to the circular base-plate D, so that 
it may be swung about a vertical axis. The feed rod E, 




Fig. 175. An American Shaper Attachment employing a Templet for 
Controlling the Shape of the Bevel Gear Tooth produced. 

operated by the regular feed movement of the shaper, is 
connected through a ratchet and hand-wheel with a worm 
and worm-gear F, connected by spur gear segments with 
the spindle head B in such a way as to swing it about its 
horizontal trunnions A, and thus feed the blank up into the 
tool. 

On the base-plate D to which the housing is gibbed, is 



FORMING THE TEETH OF BEVEL GEARS. 245 




to 



a 

a 

b 
o 



o 
a 

03 

o 

> 

PQ 

-a 



c3 
> 



a; 



t^ 
t^ 



CD 



^ 



246 GEAR-CUTTING MACHINERY. 

attached a holder G to which the former or templet is fas- 
tened. The roll which bears on this templet is held in a 
roller slide J , which is connected with the segment gears 
which swing the head in such a way that, as the blank is 
fed upward into the work, the roller slide is fed downward, 
carrying the roller along the face of the templet. Since 
the roll and roller slide are supported by the housing C, the 
templet moves the housing about its vertical axis, in con- 
junction with the swinging of the head about its horizontal 
axis, so as to produce the proper shape of tooth. The roll 
is held in contact with the templet by lever K, one end of 
which carries a weight, while the other bears on the roll 
stud. For shaping the other sides of the teeth, the templet 
is fastened on the other side of holder G, and the bent lever 
K is reversed so as to press the roll against the templet in 
its new position. A stop is provided which releases the 
automatic feed and quickly returns the head, so that the 
tool clears the work as soon as the cut has been made to 
the proper depth. We understand that Mr. Mill has de- 
signed an automatic machine operating on the same 
principle. 

In Fig. 178 is shown a German bevel gear shaping attach- 
ment, the invention of Prof. Moritz Kroll of the Govern- 
ment Trade School of Pilsen. This device is also designed 
to be mounted on the shaper table. It has a base-plate to 
which are attached two standards, F and F^, having bear- 
ings for the trunnions on head B, which may be adjusted 
about these trunnions to the desired cutting angle by 
means of a worm, and worm sector E, fast to F^. The 
work is divided by the index plate antl adjustable crank 
shown, operating a worm meshing with the index worm- 
wheel on the rear end of the work spindle A. This index 
mechanism is supported on an arm, whose lower forked 
end is seen at /. The contact points on either side of this 



FORMING THE TEETH OF BEVEL GEARS. 247 

arm, as desired, may be made to bear under spring pressure 
on cam M, which is pinned to gear Q, in mesh with gear D, 
which is in turn keyed to the shaft C, carrying the worm 
engaging with sector E. All this mechanism is mounted on 
swinging head B, excepting E, which is pinned to standard 



F 

^ 2* 



From this it will be seen that the work may be swung 



/.\A 




Fig. 178. Shaper Attachment devised by Professor Kroll, in which 
Circular Templet is used for forming the Teeth of Bevel Gears. 

up into the shaper tool about the trunnions on head B by 

operating shaft C. 

As the work is thus swung upward, gear Q is revolved, 
and with it cam or templet M, which rocks the lower end 
of lever I and with it the work. Templet M is so shaped 
that this rocking movement, in conjunction with the up- 
ward swinging of the blank, causes the point of the tool in 
the shaper to produce the required outline of tooth. In 
this, as in the previous cases, the point of the tool is set to 



248 GEAR-CUTTING MACHINERY. 

travel along a line which, if i^roduced, would meet the 
intersection of the axis of the work spindle and the axis of 
the trunnions, about which the head rocks. It is possible, 
by providing suitable change gears between cam M and 
w^orm shaft C in place of the fixed gears shown, to use the 
same cam or templet M for cutting a large range of gears, 
it not being necessary in that case to have one for each 
tooth used. 

Machines for Shaping or Planing the Teeth of 
Bevel Gears by the Templet Principle. 

In this country the templet principle is represented com- 
mercially by a single machine, that built in various sizes and 
designs by the Gleason Works, of Rochester, N. Y. This 
machine is illustrated in Fig. 179. The tool is carried by a 
holder reciprocated by an adjustable, quick-return crank 
motion. The slide which carries this tool-holder may be 
swung in a vertical plane about the horizontal axis on 
which it is pivoted to the head, which carries the whole 
mechanism of tool-hokler, slide, crank, driving gearing, etc. 
This head, in turn, may be swung in a vertical axis about 
a pivot in the bed. The circular ways which guide this 
movement are easily seen in the illustration. The inter- 
section of the vertical and horizontal axes of adjustment 
(which takes place in mid air in front of the tool slide) is 
the point in Fig. 162, where the templet principle is shown 
in diagrammatic form. The apex of the pitch cone of the 
bevel gear must be brought to this point 0. The blank is 
mounted on a spindle carried by a head which is adjust- 
able in and out on the top of the bed of the machine so 
that the apex of the cone of the gear may be brought to 
this point by means of the gauges which are a part of the 
equipment of the machine. The work spindle is provided 



FORMING THE TEETH OF BEVEL GEARS. 249 

with an indexing mechanism, which operates automatically 
as do all the other functions of the machine. 

Three templets are used, mounted in a holder attached to 
the front of the bed, on the opposite side from that shown. 
The first of these templets is for ''stocking" or roughing out 




Fig. 179. Gleason Templet-controlled Bevel Gear Planing Machine. 



the tooth spaces. It is simply a horizontal straight-edge on 
which rests a roller, attached to the outer end of the slide on 
which the tool-holder reciprocates. With the work and 
tool set properly, the whole tool-carrying head is swiveled 
about the vertical axis, feeding in at each stroke of the 
blade deeper and deeper, until the space has been properly 
roughed out. After each tooth space has been gashed in 



250 GEAR-CUTTING MACHINERY. 

this fashion, the templet holder is revolved to bring one of 
the formed templets into position, and a tool is set in the 
holder so that its point bears the same relation to the shape 
of the tooth desired as the cam roll does to the templet. 
The head is again fed in by swinging it around its vertical 
axis, during which movement the roll runs up on the sta- 
tionary templet, swinging the tool about its horizontal axis 
in such a way as to duplicate the desired form on the tooth 
of the gear. One side of each tooth being thus shaped 
entirely around, the holder is again revolved to bring the 
third templet into position. This has a reverse form from 
the preceding one, adapted to cutting the other side of the 
tooth. A tool with a cutting point facing the other way 
being inserted in the holder, each tooth of the gear has its 
second side formed automatically as before, completing the 
gear. 

The swinging movement for feeding the tool and the 
indexing of the work are taken care of by the mechanism 
of the machine without attention on the part of the oper- 
ator. The swinging feeding movement about the vertical 
axis is effected by a cam and slotted link motion which 
may be adjusted to any degree of angular movement 
required. The head may be adjusted angularly with 
respect to its feed to agree with the pitch angle of the gear 
being cut. 

The formers or templets for the Gleason machine are 
made by a molding-generating process, described by Mr. 
Fred Miller in a paper in Vol. 22 of the Transactions 
of the American Society of Mechanical Engineers. 

A French machine, built by Usines Bouhey, 43 Avenue 
Daumesnil, Paris, is shown in Fig. 180. While it operates 
on the templet principle, the movement for producing the 
desired outline is somewhat different from that employed 
in the Gleason machine previously described. Instead 



FORMING THE TEETH OF BEVEL GEARS. 251 

of applying to the tool the movement derived from the 
templet, it is appHed to the work, in a manner which 
will be evident from the illustration and the following 
description : 

The cutting tool is carried by an overhanging arm, at 
the top of the frame, operated by the slotted crank shown. 
The work spindle carrying the wheel to be cut, the index- 




FiG. 180. The Bouhey Tempiet Planing Machine, in which Provision is 
made for the Cutting of Twisted Teeth. 



ing worm-wheel, automatic dividing apparatus, etc., are 
carried on brackets attached to a swinging sector. The 
work spindle is so arranged that it may be adjusted longi- 
tudinally, to bring it into coincidence with the axis about 
which the sector is adjusted. The indexing mechanism 
is attached to a frame which is free to swing under the 
influence of the templet, which is attached to the upper 
end of an adjustable arm carried by this frame, and is 



25:2 GEAR-CUTTING MACHINERY. 

located in a position to bear on a fixed guiding plate sup- 
ported by the bed of the machine. It is held in contact 
with it by a weight and cord. 

The action is as follows: The wheel, properly mounted 
on its arbor, is swung upward toward the reciprocating 
tool by a worm feed movement, applied t(^ worm-wheel 
teeth cut in the periphery of the sector. While this angu- 
lar feeding movement is in progress, a variable rocking is 
imparted to the entire indexing mechanism, work spindle 
and work, through the action of the templet on the sta- 
tionary guide plate. It is this variable motion, controlled 
by the templet, which produces the desired outline on the 
tooth. When the correct depth of tooth has been reached, 
the feed is automatically tripped and the sector returned 
to its original position. The work is then indexed, the 
forward feed automatically reengaged, and the cycle of 
operations continued until all the teeth are finished on 
that side, and the machine is stopped by the operator, and 
reversed for completing the teeth. The movements thus 
appear to be identical with those of the attachment in 
Fig. 174, but are performed automatically. 

A unique provision of this machine is that made for cut- 
ting bevel gears with twisted teeth, as shown in Fig. 180. 
It consists simply in providing for a positive connection 
between the indexing mechanism and the crank-shaft 
driving the tool slide, through the medium of change gears, 
so that the work and crank rotate in unison at the proper 
ratio to give the number of teeth desired in the work. 
Since the stroke then takes place while the work is rotat- 
ing, a twisted form of tooth is produced. This tooth has 
the same outline (when seen at the ends) as when a straight 
tooth is being cut by the usual method. For cutting 
another gear of any angle to mesh with a gear cut this 
way — such, for instance, as the one shown in the engrav- 



FORMING THE TEETH OF BEVEL GEARS. 



253 



ing — it is only necessary to reverse the connection 
between the crank and the work so that rotation takes 
place in the opposite direction, and to set the sHde and 
the templet for the new angle and the new tooth. This 
being done and the length of the stroke being the same, 




Fig. 181. The Greenwood & Batley Templet Bevel Gear Shaping 

Machine. 

the teeth cut will exactly correspond in curvature with 
those previously cut in the mating gear. 

Twisted tooth bevel gears are almost unknown in 
America, but have found considerable use in Europe, 
where twisted tooth gearing of various kinds is in much 



254 GEAR-CUTTIXG MACHINERY. 

greater favor than here. The teeth of gears thus made 
are not made to a true conical heUx, since the motion is 
modified by the cranlv movement. All that is required, 
however, is that the curves of the gear and pinion should 
match. This requirement is met in this machine. 

An EngUsh machine, built by Greenwood & Batley, Ltd., 
Albion Works, Leeds, is shown in Fig. 18L The action 
and general arrangement of the machine are almost iden- 
tical with that of the previous case, excepting that no 
provision is here made for cutting twisted teeth, A com- 
parison of the two tools serves well to show the wide 
variation in details resulting when two designers inde- 
pendently work out the same idea. Aside from the dif- 
ference in details, there are two salient changes in the 
mechanism. One of these relates to the feed, which is of 
the ratchet type, driven from a slotted disk. The other 
change relates to the mounting of the head, which is 
carried on two superimposed swiveling sectors, which 
pivot on a common center whose axis meets the Hne of 
travel of the cutting tool. The outer sector is adjustable 
on the face of the inner one to suit the angle of the wheel 
being cut while the feed movement is applied to the 
latter. Except for the particulars enumerated, the action 
is identical with that of the Bouhey machine. 

In Fig. 182 is shown still another machine with the 
same relations between the tool, the -work and the temp- 
let. As may be seen, however, the design is so different 
that there is no resemblance between it and those shown 
in Figs. 180 and 181. The tool is carried by a ram recip- 
rocated by a mechanism similar to that used in a crank- 
driven shaper; the whole arrangement of the machine, in 
fact, resembles that of a shaper and is structurally de- 
rived from it. The work is carried on a spindle mounted 
in a frame hung about a horizontal axis from pivots seated 



FORMING THE TEETH OF BEVEL GEARS. 255 

in the arms shown projecting from either side of the head 
of the machine. The work is adjusted on the arbor to 
bring the apex of the pitch cone into the horizontal axis 
through the trunnions. A rigid outboard support for the 
work arbor is furnished, as shown. 



Fig. 182. The Oerlikon Single-Tool Templet Bevel Gear Shaper. 

The frame carrying the work is swung upward about 
the horizontal trunnions by a movement operated by the 
tooth sectors shown on each side, which are engaged by 
pinions on a horizontal shaft, connected, in turn, by gear- 
ing with a ratchet disk seen at the side of the head. From 
this the feed movement is obtained. Stops are provided 



256 GEAR-CUTTING MACHINERY. 

on the face of the ratchet disk which hmit the swinging 
feed movement; and actuate mechanism for returning the 
work rapidly when the cut has been completed, so that 
the tool is clear for indexing the blank. When the index- 
ing has taken place, the upward feed is again automatic- 
ally thrown in. As in the Greenwood & Batley machine, 
the entire dividing mechanism is attached to a bracket 
carrying an adjustable arm to the upper end of which the 
templet is attached. By means of springs this templet 
may be caused to bear on adjustable contact surfaces at 
either side, depending on which side of the tooth is being 
cut. The templet, bearing on the guide attached to the 
head of the machine on the side farthest from the ob- 
server, is somewhat imperfectly shown in the engraving. 

We think it will be agreed that this tool gives evidences 
of careful design and construction. It has a decidedly 
rugged and business-like look. It is built iDy the Societe 
Suisse pour la Construction de Machines-Outils Oerlikon, 
Oerlikon pres Zurich, Switzerland. 

Fig. 183 shows another templet machine, built by the 
same firm. The head carrying the slides is fed inward about 
a vertical axis, as in the Gleason machine. The swivcl- 
ing movement of the tool slide about the horizontal axis 
is also similar to the Gleason machine, but the two are 
differentiated in their action by the provision of a second 
slide and tool-holder, both pivoting about the same hori- 
zontal axis. The movement which the templet imparts to 
the upper slide is duplicated on the lower one, though in 
the reverse direction, so that the same outline is formed 
on each side of the tooth simultaneously. Besides the use 
of the two tool slides, this machine differs from the Glea- 
son in having the head carrying the work spindle and the 
automatic indexing mechanism, swivel for adjusting to 
the angle of the work, about the same vertical axis around 



FORMING THE TEETH OF BEVEL GEARS. 25T 

which the feeding movement of the cutter shde head takes 
place. This tool was designed by its builders to provide 
a maximum of accuracy and rapidity for work within its 
range. 

A firm in Budapest, Hungary, whose name translated 
into English reads "Small Arms and Macliine Factory 




Fig. 183. Oerlikon Bevel Gear Cutter operating on the Templet 
Principle, and using Two Tools Simultaneously. 

Company, Ltd.," has built for a number of years the 
templet bevel gear planer shown in Fig. 184. In this 
machine the work spindle is adjustable for the pitch cone 
angle, by moving it in a concave circular seat in the bed. 
This seat keeps the axis of the work spindle always in 
line with the horizontal axis of the swiveUng adjustment. 



258 



GEAR-CUTTING MACHINERY. 



The outer end of the work arbor is supported hi a yoke 
•which swivels about this axis. The mechanism on the 
upper part of the machine is the tool head, which carries 
two crank-driven sUdes, each of which carries a tool. 




Fig. 184. A Hungarian Templet Bevel Gear Planer. 

These sHdes are confined by guides which are pivoted 
about an axis passing through the apex of the pitch cone. 
The whole mechanism swivels about the horizontal axis 
passing through the same point. As the tools are swung 
down into the teeth about this horizontal axis, they are 



FORMING THE TEETH OF BEVEL GEARS. 259 

spread apart about the vertical axis by the action of 
fingers on each tool slide guide, which bear on opposite 
sides of a suitably formed templet, held in the templet 
holder at the upper right of the machine. The swinging 
downward of the tool sHde mechanism is accompHshed by 
a revolving nut on the swiveUng screw which connects 
this mechanism with the bracket to which the templet is 




Fig. 185. The Browning Templet Bevel Gear Planer. 

clamped. This latter is held in slides which are adjust- 
able for both vertical and horizontal movement. In 
having the tools swivel about both axes while the work 
remains stationary, this machine resembles the Gleason 
machine shown in Fig. 179. It is not, however, fully 
automatic. 

The templet machine shown in Fig. 185 is the design of 
Earl H. Browning, of the Browning Engineering Works, 



260 



GEAR-CUTTING MACHINERY. 



Cleveland, (). As in Fig. 183, two tools are used, each 
mounted in separate slides which are swiveled about a com- 
mon horizontal axis passing through the apex of the pitch 
cone of the gear to give the desired outline to the tooth. 
This swiveling of the cutter sHdes under the action of the 
templet takes place simultaneously with the swinging of 
the work-carrying head about a vertical axis. That is to 
say, as the tooth of the gear is swung in between the 




Tig. ISO. Detail of the Browning Machine, showing the Two 

Tool-Holders. 



points of the tools the latter are opened up with the proper 
movement to give the desired tooth outline. As the 
points of both tools travel toward the apex of the pitch 
cone of the gear, the outline of the templet is reproduced 
on a decreasing scale from the large to the small end of 
the tooth. In the details of the design this machine is 
original. One of the points of novelty is the use for the 
indexing mechanism of the quick change gear box seen 
on the work spindle head in Fig. 185. This gear box. 



FORMING THE TEETH OF BEVEL GEARS. 261 

in combination with a further change of four ratios, gives 
the entire range for cutting any ordinary number of teeth 
without the use of loose change gears. The changes of 
speed and feed are also effected by quick change gear 
boxes. Fig. 186 shows a face view of the cutter slides, 
with the tools in place in the tool-holders. In this machine, 
the templet, which is not here shown, is in the form of a 
cylindrical cam with two grooves, each of which controls 
a roller attached to the outer ends of the tool slide guides, 
which are thus controlled. 

A Machine for Milling the Teeth of Bevel 
Gears by the Templet Principle. 

In Fig. 187 is shown the principle of a templet bevel gear 
planing machine differing in many respects from any of 
those previously shown. This principle originated with 
Mr. Charles DeLos Rice, of Hartford, Conn., and the ma- 
chine he designed, incorporating it, is much used for cutting 
chainless bicycle gears, though it is not now on the market. 
The differences consist principally in the form of templet 
used, and in the form of the follower and the cutting edge 
of the tool. In other templet machines the follower which 
makes contact with the templet is presumably a point, as 
should also be (to insure theoretical exactness) the cutting 
point of the tool. In reahty, of course, the outUnes of both 
these members are rounded, a roll being generally employed 
for making the contact with the templet, and a round-nose 
tool being used for doing the cutting. Theoretical accuracy 
could be obtained under these conditions if the shape of the 
templet were made to allow for the diameter of the roller 
which follows it (as is the case in making templets for the 
Gleason machine, at least) and if the shape of the point of 
the tool is also considered. The latter, however, should 



262 



GEAR-CUTTING MACHINERY. 



grow continuously smaller in radius as it approaches the 
small end of the tooth, in the same scale with the decreased 
size of the tooth itself; and similarly it should grow larger 
as it approaches the large end. As it remains the same size 
all the time, of course, a slight error is introduced — so 
slight, however, as not to introduce anything except a neg- 
Hgible inaccuracy. 

In the Rice machine the copying of the templet is done 
with theoretical precision. Both the guiding and the cut- 




FiG. 187. 



Model illustrating the Principle of tlie Rice Machine shown 
in Fig. 188. 



ting edges are plane surfaces, and being such, obviate the 
necessity for a change of scale in cutting outlines at differ- 
ent points of the stroke. Fig. 187 shows a model of the 
movement employed, especially made for the purpose of 
illustration. The templet, A, used, is a complete gear of 
the same proportions as the work to be cut, but on a larger 
scale. It is mounted on a spindle fast to the blank B. 
This spindle is carried by a swinging bracket C, pivoted 
about an axis at right angles to that of the work, and pass- 
ing through the apex of the pitch cone of the work and 



FORMING THE TEETH OF BEVEL GEARS. 263 

master gear. The sketch of the inotlel shows a disk E 
mounted on a fixed horizontal spindle, entering one of the 
spaces which have been cut in the blank. The acting sur- 
face of the disk is in the plane of the vertical axis about 
which bracket C swings. In the same plane is the acting 




Fig. 188. The Rice Bevel Gear Milling Machine, which forms the Teeth 
from a Master Gear on the Templet Principle. 

surface of a fixed stop or guide plate D, which, as shown, 
is mounted on the same pedestal as the spindle of the disk 
and enters the space cut in the master gear in the same way 
that the disk enters the space between the teeth of the work. 
If the teeth of the master gear be pressed against the act- 



264 GEAR-CUTTING MACHINERY. 

ing side of the fixed stop, while the bracket supporting the 
master gear and the work is rocked about its vertical axis, 
it is evident that the stop will roll about the face of the 
tooth of the master gear or templet, making line contact 
with it, while the face of the disk will act in an identical 
manner, though on a smaller scale, with relation to the 
tooth of the work. If the disk be replaced with a cutter of 
the same diameter, and with a cutting face in the same 
plane as that occupied by the acting face of the disk, the 
rocking of the bracket about its vertical axis will evidently 
cause the cutter to mill out a tooth face identical with that 
of the templet or master gear, but on a smaller scale. 
While this operation appears to have the ear marks of the 
generating process, it operates on the templet principle in 
reality, as is shown by the description we have just given. 
The cutter is made of large diameter, as compared with the 
work, in order to give as straight a bottom to the tooth 
space as possible. The deepening of the tooth space in 
the center does not, of course, affect the accuracy of the 
working portion of the outline. 

An automatic machine in which these principles are 
embodied is shown in Fig. 188. The mechanism is too 
intricate to be described without the use of a considerable 
number of line drawings and an extended description, so we 
will content ourselves with enumerating the movements 
which the mechanism effects. The master gear governs the 
tooth spacing, the tooth thickness, and the tooth form. The 
master gear and a previously-gashed blank being mounted 
in position in the machine with the guide plate and cutter 
positions and other adjustments properly made, the mech- 
anism is started. The cam movements provided first feed 
the master gear and work spindle ujnvard until the cutter 
is in to depth and the stop bears against the face of tlie 
master gear. The bracket carrying them is then rotated 



FORMING THE TEETH OF BEVEL GEARS. 265 

about its vertical axis until one face of one tooth of the 
blank is completed. The work is now dropped down out 
of the way, and the spindle, with the blank and master 
wheel, are indexed one revolution, after which they are 
again raised, repeating the same operations as before. 
This is done repeatedly until the whole gear has been cut 
around on one side of all the teeth. When this has been 
done, the machine stops and the attendant rotates the seg- 
ment of a hand-wheel rim seen encircling the front pillar 
of the machine. Through the link connections on this rim, 
the fixed gage and the cutter are each shifted axially a dis- 
tance equal to their thickness, so as to bring them to posi- 
tions to work on the other side of the tooth. The automatic 
mechanism for swinging the work spindle is also changed 
by the same movement, so that it swings in the other direc- 
tion. The mechanism is then started up and the other 
sides of all the teeth are finished. 

An interesting point in the product of this machine is that 
the gears produced are accurate copies of the master gear 
on a smaller scale. It is thus possible where bevel gears are 
to be made in large quantities, to make the master gear and 
pinion, and run them together under conditions severe 
enough to test their suitability for the work the smaller 
gears are to perform. Such corrections as may be required 
being made in these large gears, assurance is given that the 
smaller gears will behave in a satisfactory way. The prin- 
ciple of this machine could, of course, be adapted to a ma- 
chine for general use, by using as a templet but a single 
tooth of the master gear, instead of employing an entire 
wheel, as here shown. It was at one time, we are informed, 
the intention of the inventor to develop such a machine, 
but so far this has not been done commercially. Obviously, 
this method of applying the templet principle cannot be 
applied to cycloidal teeth having concave surfaces. 



2GG 



GEAR-CUTTING MACHINERY. 



Machines Employing the Templet Principle for 
Grinding the Teeth of Bevel Gears. 

The grinding operation has been used in a templet ma- 
chine built by the Societe Suisse pour la Construction de 




Fig, 189. The Oerlikon Templet Gear Shaper of Fig. 182, arranged with 
Grinding Wheel for finishing Hardened Bevel Gears. 

Machines-Outils Oerhkon, Oerlikon pres Zurich, Switzer- 
land, and shown in Fig. 189. As may be seen, it is a modi- 
fication of their regular templet planing machine, previously 
shown in Fig. 182. The change consists merely in replac- 



FORMING THE TEETH OF BEVEL GEARS. 267 

ing the cutting point of the tool with the edge of a grinding 
wheel, carried on the head of the ram, and provided with 
suitable means for chiving it at the proper speed. Under 
these conditions, the edge of the wheel shapes the teeth of 
the gear to the form of the templet provided. The builders 
state that by the employment of special wheels which they 
have developed for the purpose, it is possible to cut clear 
around a large gear without a perceptible change in the 
condition of the cutting edge, or a corresponding change in 
the profile of the tooth produced. If this is so, the greatest 
objection to the grinding process for gear cutting of any 
kind is largely obviated. The purpose of the machine is, 
of course, the finishing of the teetli of hardened gears to 
remove the inevitable inaccuracies (kie to thstortion arising 
from the heat treatment. It has been found especially 
useful in automobile work. 

This Swiss firm has done especially noteworthy work in 
the buikling of machines for cutting bevel gears. The three 
we have illustrated. Figs. 182, 183 and 189, and one later 
in Fig. 217, for rough -milling bevel gears, do not by any 
means exhaust their list of machines built for forming the 
teeth of gears of this type. Among other Oerlikon designs 
may be mentioned two of great interest, described in the 
paper by Mr. Fred. J. Miller, to be found in Volume 22 of 
the Transactions of the American Society of Mechanical 
Engineers. 

Machines Working on the Odontographic Principle 
FOR Cutting the Teeth of Bevel Gears. 

A machine operating on the odontographic principle, in 
which the point of the tool is guided by mechanism which 
very nearly reproduces the theoretical shape, is shown in 
Fig. 190. It is built by Officina Meccanica Ing. E. Dubosc, 
Via Principi d'Acaia, 62, Turin, Italy. In this machine, as 



268 



GEAR-CUTTIXG MACHINERY. 



may be seen, the work spindle is horizontal and is indexed 
by a dividing wheel of large diameter. The work arbor 
is supported at the outer end in a stirrup held in the swing- 




FiG. 190. The Dubosc Bevel Gear Planing Machine, cutting Invokite 
Teeth by the Odontographic Principle. 

ing tool frame, this support making it possible to do heavy 
and rapid cutting. The work is adjusted by means of suit- 
able gages until the apex of its pitch cone lies in the center 



FORMING THE TEETH OF BEVEL GEARS. 269 

line of the journals provided (at the top and bottom of the 
main casting of the machine) for the trunnions of the frame 
which swings about the work on a vertical axis. This frame 
carries most of the mechanism of the machine, and is pro- 
vided with pivots in a horizontal axis, in the same plane 
with the vertical axis, about which swings a counter-bal- 
anced arm having guides for the tool slide. A tool may 
thus be set to have a reciprocating movement in any plane 
containing the apex of the pitch cone of the work. This 
being the case, if suitable mechanism for effecting it is pro- 
vided, the tool may be made to plane a conical surface, 
vanishing at the center of the horizontal and vertical axes, 
and determined by any line drawn on the surface of a sphere 
having the same center. In this respect it resembles all 
templet and odontographic machines, which arc distin- 
guished from each ctlier only in the means provided for 
guiding the tool, as shown in Figs. 1()1 and 1(52. 

In the machine in question, the odontographic mechan- 
ism provided produces teeth of involute form. This mech- 
anism (which is obscured in Fig. 190) is shown in diagram- 
matic form in Fig. 191, in two positions. We cannot take 
the space here to describe why the mechanism produces 
a curve of almost absolutely true involute form, nor can 
we enter into the details of the connections by which the 
movements effected by this mechanism are transferred to 
the point of the tool, as this would require a chapter in 
itself. It can only be said the pinion A is connected with 
a worm meshing with a segment of a worm-wheel fast to 
the base of the machine, by means of which the frame 
carrying the mechanism and the tool is rotated about its 
vertical axis. This pinion meshes with the segmental gear 
B, which carries a crank-pin C, angularly adjustable for a 
certain amount about the center of the gear. A connecting- 
rod D, adjustable for length, connects crank-pin C with a 



270 



GEAR-CUTTING MACHINERY. 



second pin E attached eccentrically to a disk F, eccentri- 
cally seated in turn in a crank whose center is G. Disk F, 
with crank-pin E, may be adjusted for various angular 
positions about the center of the disk by worm H. Crank 
G is connected with mechanism for swinging the tool sHde 
in a vertical plane about its vertical axis, the whole mech- 
anism thus serving to connect the swinging movements 
of the tool about the horizontal and vertical axes. By 





Fig. 191. The Odontographic Mechanism of the Dubosc Machine at the 
Beginning and End of the Cutting Action. 



setting C according to graduations at various angular 
positions with relation to B, and by setting E at various 
positions by the rotating of disk F, and by adjusting the 
length of connecting rod D, the movements about the 
horizontal and vertical axes may be so connected as to 
produce tooth outlines of nearly theoretical accuracy. 

This apparatus, as described, determines the form of the 
tooth. Change gears provided between G and the vertical 
movement which it accomplishes, and A and the horizontal 
movement with which it is connected, alter the scale of the 



FORMING THE TEETH OF BEVEL GEARS. 271 

outline — that is, adapt it to a large tooth or a small tooth 
as may be required. Still other change gears are provided 
for the indexing, which is automatic, as are all the functions 
of the machine for completely forming one side of all the 
teeth of the gear. The shape that can be given varies from 
the straight side of the rack tooth (which is used for all gears 
having more than 150 teeth), to small bevel pinions with 
undercut flanks in which a reverse motion has to be given 
to the movement about the horizontal axis. The tool is 
provided with mechanism for cutting on both the forward 
and back stroke on work that is large enough to admit 
this. 

We are informed by the English licensees of the Dubosc 
patents, Messrs. Sehg, Sonnenthal & Co., 85 Queen Victoria 
Street, E. C, London, England, that the builders of the 
tool are preparing a new design, embodying a number of 
improvements in the mechanism. 

The only other odontographic machine the writer is 
acquainted with is built by Smith & Coventry, of Manches- 
ter, England (see Figs. 192 and 193). It is somewhat easier 
to understand than the Dubosc machine, as the curves it 
employs are simple arcs of circles. Two tools T^ and T^ are 
used, each set in separate sHdes S^ and S^ pivoted about an 
axis at the apex X of the pitch cone of the blank being cut. 
These sHdcs have rearward extensions in the form of arms 
A^ A^, ending in slotted arcs concentric with axis X. Each 
of these arms is clamped by bolts passing through the 
slotted arcs to blocks C^ and C^ sliding in horizontal guides 
on parallel bars D^ and D^. Bar D^ is supported on links E 
and E^, while bar D^, pivoted also to double-ended Hnk E, is 
supported by it and short link E.^. As link E is rocked, the 
two bars swing, one to the left and upward and the other to 
the right and downward, but with their guiding surfaces 
always parallel. As they are swung in this way, the two 



272 



GEAR-CUTTING MACHINERY. 



slides A^ and A^ are brought together or opened out, as the 
case may be. 

The rocking of this parallel linkage system is effected by a 
connection with the angularly adjustable head M, which 




o 

c3 



o3 



O 

w 



Xi 
Cu 
c3 
;-< 
fa£ 
O 

C! 
O 

O 



> 

o 
O 






Ci 



M 



carries the work spindle. This is swung inward for the feed- 
ing movement to shift the tools down the sides of the tooth 
until the full depth has been reached. To sHde M is 
clamped a circular bar N, whose rear end has teeth cut in it 



FORMLXG THE TEETH OF BEVEL GEARS, 273 



engaging with those of a sector G, which, by the bevel gear- 
ing shown, is connected with slotted arm H. This arm is 
adjustably connected with link £" by a connecting-rod /, 
which, as shown, may be altered sUghtly as to length and to 




the amount of movement given it, depending on the way in 
which it is clamped to E. From this it wih be seen that as 
the work sUde M swings around, moving the teeth of the 
blank inward toward the tools, its connection with circular 






o 



pq 



> 

o 
U 






si 



CO 
05 



O 

M 



274 GEAR-CUTTING MACHINERY. 

bar N through sector G, and the geared connections of the 
latter with arm H, operate the hnkage system E, E^, E^, and 
bars D^ and D^, with the tool-sUdes S^ and ^2 connected with 
them. By this means the tools are gradually opened out as 
the base of the tooth is approached, in such a way as to 
make their outhnes correspond to circular arcs approximate 
to the desired involutes, the circular form being determined 
by the swinging of the links E^ and E^ about their centers. 
Tables are furnished for setting J with relation to H, and 
arms A^ and A^ with relation to D^ and D^, so as to repro- 
duce on the teeth the proper outlines. 

It should have been mentioned that this machine does 
not work on the principle of completing one tooth, and then 
indexing to complete the next. The work indexes at 
every stroke of the double tools. After the first cut has 
been taken on the first tooth, the work is indexed and the 
same cut taken on the next tooth. When the work has 
been once around in this way, the tool starts in with a deeper 
cut on the first tooth again, this continuous rotation and 
gradual feeding in of the tool continuing until all have 
been simultaneously formed to the required depth and 
proper shape, being similar in this respect to the Bouhcy 
machine in Fig. 180, and the Bilgram machines shown 
later in Figs. 190 and 197. 



CHAPTER VIII. 

MACHINES FOR FORMING THE TEETH OF BEVEL 
GEARS {Continued). 

This chapter continues the discussion of machinery for 
cutting tlie teeth of bevel gears, being devoted to such of 
them as operate on the molding-generating principle. 

Finishing Bevel Gears by the Operation of 
Impression. 

In Fig. 194 is shown the only example known to the 
writer of a conunercial machine using the operation of 
impression. This machine was built by the Brown & 
Sharpe Manufacturing Company, Providence, R. I., for 
performing the finishing and correcting operations on 
bevel gears, roughed out in the special full automatic 
formed-cutter machine, previously described, and shown 
in Fig. 173; it is not a machine which finishes the gear 
directly from the blank. The impression process is, of 
course, absolutely impracticable for operations that would 
require the pressing into shape of as much metal as would 
be required in that case. 

The machine has two spindles, of which the one carrying 
the forming gear is driven by suitable belts and i)ulleys 
from the counter-shaft, while the other spindle is mounted 
in a head which, as shown, can be set at any angle with 
the first, to agree with the angle between the axes of the 
forming gear and the work being pressed into shape. The 
forming gear, instead of being a small pinion, as in Fig. 163, 
is a crown gear; this gear is chosen on account of the 

275 



276 



GEAR-CUTTING MACHINERY. 



facility with vviiich it can be accurately made, the sides of 
the teeth in the system employed being plane smfaces, as 
described in connection with Figs. 164 and 165. In the 
final operation, a forming gear thus correctly made and 
hardened so as to resist the wear brought to bear on it, 
is mounted on the belt-driven spindle and brought into 
proper engagement with the roughly formed gear mounted 




Fig. 194. Brown & Sharpe Machine for Correcting Bevel Gears by the 
Molding-Generating Principle, employing the Impression Process. 



on the other spindle. The machine is started up and the 
two are revolved together. The mechanism provided is such 
that the pair run in one direction for a certain number of 
revolutions and then reverse and run in the other direction, 
repeating the process as long as the machine is in operation. 
Meanwhile a cam mechanism operates, to jam the blank 
and forming gear together, relieve the pressure for a short 



FORMING THE TEETH OF BEVEL GEARS. 277 

space and jam them together again, repeating the process 
continuously. By this means the hardened surface of the 
forming crown gear presses out the inaccuracies in the 
work and smooths the surfaces of its teeth, which were 
cut in the machine shown in Fig. 173. 

The operation just described is the final one, however, 
and does little more than burnish the teeth. The same 




Fig. 195. Near View of the Tool and the Work in the Machine shown 

in Fig. 194. 



machine is used for a preliminary operation which does 
most of the work of smoothing out the inaccuracies of the 
formed cutter process. This employs the same movements 
in the machine, but uses a different form of crown gear, 
shown in action in Fig. 195. As may be seen, the successive 
teeth are cut off at different heights. The edges thus 
formed where the teeth are cut off, dig into the roughed- 
out teeth of the work and remove the metal from the hiffh 



278 GEAR-CUTTING MACHINERY. 

spots, while they pass freely and without action over the 
parts of the teeth which are of the correct contour. Being 
of so many different heights the whole face of each tooth 
of the work is acted on, though, of course, this is the case 
only when the number of teeth in the work and in the 
crown gear do not have a large common factor. In the 
bicycle trade for which these machines were developed, 
the gears were so designed that this contingency did not 
arise. 

Machines Operating on the Molding-Generating Prin- 
ciple, AND Employing the Planing or Shaping 
Operation. 

The mechanism illustrated in outline in Fig. 1G4 is 
one that has been employed in a number of exceedingly 
interesting and ingenious machines. The first application 
of this principle was made by Mr. Hugo Bilgram, 1231 Spring 
Garden Avenue, Philadelphia, Pa. His form of machine 
has been used for a great many years, and produces work 
whose accuracy has almost become proverbial. An 
automatic machine of this make is shown in Fig. 19G. 
The movements operate on the same principle as that in 
Fig. 1G4, but in one of the modified forms explained in the 
text accompanying that figure. This is to say, instead of 
rotating the crown gear and master gear together, the 
imaginary crown gear and, consequently, the tool, remain 
stationary so far as angular position is concerned, while 
the frame is rotated about the axis of the crown gear, 
thus rolling the master gear on the latter and roUing the 
work in proper relation to the tool. Instead of using 
crown and master gears, however, a section of the pitch 
cone of the master gear is used, which rolls on a plane 
surface, representing the pitch surface of the crown gear. 
The two surfaces are prevented from slipping on each 



FORMING THE TEETH OF BEVEL GEARS. 279 

other by a pair of steel tapes, stretched so as to make the 
movement positive, in something the same way as shown 
in Fig. 4. A still further change consists in extending the 
work arbor down beyond center of Fig. 104, mounting 




Fig. 196. Full Automatic Bilgram Bevel Gear Shaper, working on the 
Molding-Generating Principle. 

the blank on the other side of the center so that the tool, 
being also on the other side of the center, is turned the 
other side up from that shown in the diagram. All these 
movements can be followed in Fig. 196. As explained, a 



280 



GEAR-CUTTING MACHINERY. 



tool with a straight edge is used, representing the side of 
a rack tooth, and this tool is reciprocated by a slotted 
crank, adjustable to vary the length of the stroke, and 
driven by a Whitworth cjuick return movement. The 
feed of the machine is effected by swinging the frame in 
which the work spindle and its supports are hung, about 
the vertical axis of the imaginary crown gear. Suitable 




Fig. 197. Bilgram Bevel Gear Shaper as built by J. E. Reinecker. 



feed connections, index mechanisms, etc., are provided for 
convenient operation. 

This machine does not operate on the principle of com- 
pleting one side of one tooth before going to the next. It 
follows the plan adopted by the same builder in his spur 
and spiral planing machines shown in Figs. 50 and 114, 
in which the work is indexed for each stroke of the tool, 
the rolling action being progressive with the indexing 
so as to finish all the teeth at once. A little thought will 



FORMING THE TEETH OF BEVEL GEARS. 281 

show that these three Bilgram machines are identical in 
principle, with only the modifications required to fit that 
principle to the making of spur, spiral, and bevel gears, 
respectively. The bevel gear machine is the only one that 
has come into extensive use, since the bevel gear is the only 
one of the three kinds in which there is any great difficulty 
in cutting the teeth accurately enough for all practical 
purposes with formed tools. 

In Fig. 197 is shown another example of this machine, 
built under the Bilgram patents by J. E. Reinecker, of 
Chemnitz-Gablenz, Germany. 

A machine operating on the same principle is that built by 
the Ateliers de Constructions Mecaniciues ci-devant Ducom- 
mun, Mulhouse (Alsace). (See Fig. 198.) The principal dif- 
ferences between it and the Bilgram machine (aside from 
the obvious differences of the shape of the framework and 
the arrangement of the mechanism) are the link motion 
used in place of the steel tape for giving rolling movement 
to the blank, and the provision made for using two tools 
simultaneously so that both sides of a tooth are finished at 
once. This machine is not fully automatic, but is arranged 
to cut both sides of one tooth, after which it is indexed 
by hand and the sides of another tooth cut. 

The two tools are each carried in shdes of their own, in 
the center of the circular top of the table. These slides 
are independently adjusted to bring the movement of the 
straight cutting edges in fine with the plane surfaces of 
the teeth of the imaginary crown gear of Fig. 139. As 
in the Bilgram machine, the tool slides are stationary, while 
the frame carrying the work spindle is revolved about 
the vertical axis of the crown gear, a tooth of which is 
represented by the cutting edges of the tool. The swiveling 
movement of this frame is effected by a sector of a worm- 
wheel fastened to the circular table on which the frame 



282 



GEAR-CUTTING MACHINERY. 



is mounted. Suitable feeding movements and automatic 
stops are provided. 

The provision for constraining the blank to roll in the 




Fig. 198. Ducommun Bevel Gear Generator operating Two Tools. 



proper ratio with the rotation of the housing about the top 
of the column, is the most original feature of the ma- 
chine. The principle of its operation will be understood 
by reference to Figs. 199 to 204 inclusive. It will be 



FORMING THE TEETH OF BEVEL GEARS. 283 

simplest to consider the problem first from the stand- 
point of the spur gear. In Fig. 200 is shown a gear being 
cut by two tools representing a tooth space of an imaginary 
rack, in a way similar to that shown in Fig. 8. It is here 
considered, however, that the gear to be cut is rolling on 
the imaginary rack, which is stationary. The rolling 
movement of the gear is obtained by a master gear of the 





/ 


ito^i \ 


' '' R 








V 




id 


^ 


^M 




Fig. 199. 




Fig. 200. 




Kf-:i^ 



Fig. 201. Fig. 202. 

Diagrams illustrating the Action of the Ducommun Machine. 

same pitch diameter, engaging a master rack, which, in 
the end view, coincides with the imaginary rack. 

It is not necessary that a rack and master gear be used to 
give the desired rolling movement to the gear to be cut; the 
metallic tape arrangement shown for the describing- 
generating process (see Fig. 4) could be used, for instance. 
Still another method is indicated in Fig. 199. When the 
pitch circle of the master gear rolls on the pitch line of the 



284 GEAR-CUTTING MACHINERY. 

rack, as the center occupies the positions B^, B^, etc., a 
point such as K^ in the pitch circle of the master gear will 
trace a C3^cloid A\, K^, K^. A point J can be found so 
located that it will be the center of an arc very closely 
approximating the cycloid. If, therefore, instead of the 
master gear and rack, we substitute, as shown, a crank 
B^Kj^ in place of the gear, and a hnk JA\ to connect the 
crank-pin with the point J determined as above described, 
then, when the axis of the blank is given a lateral move- 
ment, the link will so restrain the motion of the crank-pin 
K^ that it will nearly follow the cycloid, and in so doing 
will give the blank a close approximation to the rotary 
motion obtaine 1 by the gear and rack in Fig. 200. 

The same process as appHed to the forming of bevel 
gears is shown in Fig. 202. The rack is replaced by a 
crown gear and the master gear is replaced by a master 
bevel gear whose axis passes through the central point 
of the crown gear. The gear to be cut is mounted on the 
axis of the master bevel gear and moves with it, and is so 
located that its pitch cone apex is at C, the center of the 
crown gear. If, then, the sides of the teeth of the crown 
gear be plane surfaces, a pair of tools with their cutting 
edges in the plane of the tooth faces of a rack space may 
be used to generate the teeth of the gear to be cut, when 
these tools are given a reciprocating motion which allows 
their cutting edges always to remain in the plane of the sides 
of the rack tooth. All this is substantially the same as 
shown in Fig. 164. The axis of the master gear and blank, 
instead of being given a rectilinear horizontal motion at 
right angles to the axis as in Fig. 200, is given a circular 
motion about vertical axis XX, so that line BC would de- 
scribe a cone if it were completely revolved. The master 
bevel gear is thus given the proper rolHng motion about the 
crown gear. 



FORMING THE TEETH OF BEVEL GEARS. 285 



By a similar approximation to that illustrated in Fig. 199, 
we may do away with the crown gear and the master bevel 
gear. The pitch circle of the master bevel gear rolls about 




Fig. 203. Vertical Section through Plane of Work Spindle. 

the pitch circle of the crown gear. In so doing, a point Ki 
in the pitch circle of the master bevel gear will, as shown 
in Fig. 201, describe a spherical cycloidal curve determined 
by points K^, K^, K^, which are the positions that point 



286 GEAR-CUTTING MACHINERY. 

K^ takes in the three positions of the pitch circle marked 
No. 1, No. 2, and No. 3 in the sketch. It must be remem- 
bered, in following this action, that all the lines shown are 
supposed to be drawn on the surface of a sphere with C 
as center. Now, as in Fig. 199, we find a point J such that 
with one point of the dividers located here, the other 
point will follow the spherical cycloid K^, K^, K^ very 
closely. We may, then, as in Fig. 199, dispense with the 
master and crown gears, replacing them with a crank or 
link Bfi^, pivoted at one end to axis BC, and joined at 
the other end at point K^ to the swing link pivoted at /. 
With this arrangement within reasonable limits, a rota- 
tion of axis BC about vertical axis XX will impart to the 
gear to be cut, through the restraining action of link JK^, 
a motion similar to that given by a master bevel gear and 
crown gear; and this will be suitable, as before explained, 
for shaping the correct form of tooth on the blank under 
the action of the two cutting tools. 

Now let us trace in the machine the action explained 
by the two diagrams. Axis BC in Fig. 202 is that passing 
through the gear to be cut in Fig. 203. The rotation of 
this axis about the vertical axis XX of the machine is 
effected by rotating the whole structure on which it is 
supported around the circular bearing provided at the 
top of the column of the machine. The table, carrying 
the structure for holding the gear blank, has a section of 
a worm-wheel formed on a portion of its periphery, which 
is operated by a worm, and suitable slow-feed, quick-return 
and automatic stop mechanisms. So much for the move- 
ment about the axis XX. For the rolling motion, which 
must be given the blank to agree with that of the master 
bevel gear rolling on a crown gear, the approximation out- 
lined in Fig. 201 is used. Link / in Figs. 203 and 204 
is hnk Bfi^ of Fig. 201. Point K in Figs. 203 and 204 



FORMING THE TEETH OF BEVEL GEARS. 287 




WMmmMmmmmmm/M////Mm 

Fig. 204. Diagram showing Arrangement of Approximating Linkage. 

is point K^ in Fig. 201. In Fig. 204 pivot K has been 
raised from the position it should occupy directly back 
of point ^p to show the construction of Hnks L. Consider- 
ing, however, that the mechanism is in its proper condition, 
when the blank is given its rotation about vertical axis XX, 



288 GEAR-CUTTING MACHINERY. 

point K^, if the proper rolling motion is given the blank, 
will trace a spherical cycloid identical with K^, K^, K^ in 
Fig. 201. To insure that point K shall follow with great 
exactness this cycloid, as the blank rolls to the left, one 
of the pair of springs shown at the lower end of link / presses 
pivot K to the bottom of the open-ended slot in link L, 
which is pivoted at point J , this point being selected in 
the same manner as point J in Fig. 201. It will thus be 
readily understood that the rotary and rolling motions 
required for the blank are very closely approximated. 
Of course the cut is not started from the middle as we have 
been considering. The blank is first swung to the extreme 
right, for instance, so that it clears the tools. Under those 
circumstances the pivot K will bear on the bottom of the 
open-ended slot in the right-hand link L, being held there 
by the pressure of the right-hand spring. When it reaches 
the central position shown in Fig. 202 it will be under the 
restraining influence of both links L. As it continues to 
swing toward the left it will come under the control of 
left-hand link L and the left-hand spring. 

An English machine of the molding-generating type 
operating on the shaper principle is shown in Fig. 205. 
Here the axes of both the work and the imaginary crown 
gear are stationary, the blank and the tool swinging about 
these axes. The proper ratio of rolling movement of these 
two parts is obtained by change gears. The machine has 
two distinctive features not found in other generating 
machines, so far as the writer is aware. One of them is 
the provision made in the mechanism for automatically 
gashing the wheel preparatory to the finishing generating 
cut. In this operation the blank is swung around into the 
reciprocating tool until the proper depth has been cut. It 
is then returned rapidly and the work is indexed for the 
next cut, which is taken in the same way. This swinging 



FORMING THE TEETH OF BEVEL GEARS. 289 

of the work into the cutter and back again is effected by the 
adjustable crank shown at the front of the machine, 
which has a slow ratchet feed for cutting to depth and a 
quick movement for returning. This same crank mechan- 
ism is used without the slow ratchet feeding for bringing 
the cutter into depth for starting the generating cut, and 




Fig. 205. The Churchill Bevel Gear Generating Machine, in which 
Provision is made for Modifying the Teeth to avoid Interference. 



swinging it back at its completion to clear for the auto- 
matic indexing in the finishing operation. The other 
distinguishing feature of this machine is the provision 
made for correcting the teeth for interference. In other 
generating;' machines this correction is made by altering 
the addendum and dedendum of the gear and pinions 
in cases where it is necessary. In this case it is clone by 



290 GEAR-CUTTING MACHINERY. 

modifying the tops of the teeth the same as in the standard 
shapes for spur gears. To accomplish this the swivehng 
movement of the tool slide is retarded as the tool is leaving 
the point of the tooth. A slotted cam groove will be seen, 
cut in a sector which is fastened behind the outer end 
of the swinging tool slide. This cam groove controls the 
movement of a short slide, which, in turn, by means of 
the diagonal groove and block shown, gives a relative 
movement between the slide itself and the sector on which 
it is mounted. This movement is sufficient to trim the 
tops of the teeth as required. The builder of this machine 
is the Churchill Machine Tool Company, Ltd., Man- 
chester, England. 

A French machine of the type we have been considering, 
built by H. Ernault, 169 Rue d'Alesia, Paris, is shown in 
Fig. 206. It was designed by M. Monneret, and shown 
at the Paris exhibition in 1900. The writer is not sure 
that it is being manufactured for the trade at the present 
time. It is of such interest, however, as to warrant 
illustration and description. 

This machine is identical in its operation with the 
typical mechanism shown in Fig. 164, in that the axes of 
the work and of the imaginary crown gear are fixed in 
position, and are rotated in the proper ratio with each 
other to give the desired rolling movement of the tool and 
the blank on each other. The cutter sHde is mounted on 
what resembles the head-stock of a lathe, at the right-hand 
side of the machine in the illustration. It is driven by a 
crank seen through the opening at the front of the shde. 
The tool is carried on the holder at the back upper end 
of the slide, and is provided with automatic means for 
positively relieving it on the back stroke. 

To understand how this tool shde is rolled about its 
axis in unison wijth the rolHng of the blank it is first 



FORMING THE TEETH OF BEVEL GEARS. 291 

necessary to state that this machine will cut helical gears 
only, this being due to the fact that the crank-shaft and 
the blank are connected positively by change gearing, so 
that the blank rotates continuously, resembUng in this 
particular the arrangement provided on the Bouhey 




Fig. 206. The Ernault Bevel Gear Generating Machine, which cuts 
Gears with Twisted Teeth. 

machine for making, when required, gears of this kind 
by the templet process. Unlike the Bouhey machine, 
however, the one we are describing cannot be used for 
making straight-tooth bevel gears; and, since the blank 
has to have imposed upon it a rotary motion in unison 



292 GEAR-CUTTING MACHINERY. 

with the rolhng of the tool sUde, and in adcUtion to the 
rotating motion due to its connection through the change 
gears with the tool-shde crank-shaft, a differential move- 
ment has to be introduced for combining the two. 

Change gears are set for the number of teeth to connect 
the crank-shaft and the indexing worm at the rear of the 
work spindle, through a train of positive gearing and 
shafts. The rolling movement of the blank (and of the 
tool slide about its axis) is driven by a cam and ratchet 
movement operated by the spur gearing leading from 
the work spindle at the left of the machine in the engraving. 
This ratchet-driven motion is connected by bevel gears 
with a screw which shifts, in the direction of its axis, a 
cradle or yoke in which is confined the index worm for 
giving the rotary movement to the blank. This worm is 
splined upon its shaft, so that it transmits to the work 
through its longitudinal motion a rolling movement 
derived from the ratchet feed, and a continuous rotary 
movement derived from the change gearing and the crank- 
shaft. These movements are combined without inter- 
fering with each other, and either may be started or 
reversed independently. It will be seen that the mechan- 
ism is exactly identical in principle with that described 
for the Reinecker worm gear bobbing machine in Fig. 143. 

The same ratchet mechanism that shifts the indexing 
worm axially is connected by the train of gearing shown 
with a vertical shaft passing down through the center of 
the angular adjustment of the work slide, where it is con- 
nected with a screw, shown diagrammatically at A in 
Fig. 207. This screw is supported in bearings connected 
with the work slide in such a way that, as the latter is 
adjusted to the angle of the gear being cut, the screw is 
swiveled with it, being always at right angles to the axis 
of the work spindle. The nut B, which encircles this 



FORMING THE TEETH OF BEVEL GEARS. 293 



screw, is pivoted to a sliding block C, which is dovetailed 
to slide D. D in turn slides in guiding ways E in the 
direction xy. Slide D is fastened to a rack meshing with 
a pinion, connected by shaft and gearing with mechanism 
for rocking the tool slide, the whole arrangement furnish- 
ing the means by which the rolling of the blank effects the 
corresponding rolling of the imaginary crown gear and the 
work in unison. 





Fig. 207. The Mechanism by which the Proper Ratio of RolHng Move- 
ment for the Blank and Tool is obtained for the Machine in Fig. 206. 

The ingenious feature of the mechanism in Fig. 207 is 
the way in which the proper ratio of movement for the 
rolling of the work and the tool is assured. When the axes 
of the work and of the imaginary crown gear are set in 
the same straight line, as would be required when cutting 
a crown gear, the axis of screw A is by that setting shifted 
until it is parallel with xy, and thus the movement of D 
on xy is the same as that of the nut B along the screw, 
and the work, consequently, rolls in unison with the tool 



294 GEAR-CUTTING MACHINERY. 

slide. If, on the other hand, the work spindle is adjusted 
to angle a with the axis of the crown gear, the mechanism 
will take the position shown in the engraving, and the 
screw, when moving the nut a distance a, will move slide 
D on ways E a smaller distance h, resolving the motion a 
into two components, h and c. Of these two, 6 is in 
exactly the right proportion to a to give the rolling move- 
ment required for the tool, and it is transmitted to the 
tool slide by the motion described. This, it will be seen, 
does away with the necessity for adjusting the rolling 
movements separately as required for all other generating 
machines. 

In Fig. 208 is shown an American machine of the mold- 
ing-generating type employing the planing or shaping 
operations. It dificrs from the previous machines of this 
kind we have described in employing two tools, one on 
each side of the tooth, resembhng in this respect the 
templet planers shown in Figs. 183 to 186 inclusive. This 
tool is identical with the previous one and with the 
mechanism in Fig. 164, in having the axes of the tool 
slides and of the blank fixed in relation to each other dur- 
ing the operation, the tool-holders and the blank rocking 
about their axes to give the rolling movement for cutting. 
The connections, however, between the blank and the 
slide are entirely different, and the tools finish each tooth 
of the work complete before they commence on another. 
The rocking is effected by means of segments of an actual 
crown gear and master gear. The segment of the crown 
gear, seen beyond the work in the illustration, is perma- 
nently attached to the face of the rear of the cutter slide 
frame, while the segment of the master gear (of which 
there are several furnished with the machine, the one 
used being chosen to agree with the angle of the gear to 
be cut) is clamped to the semicircular arm pivoted at 



FORMING THE TEETH OF BEVEL GEARS. 295 



the outer end of the machine at one side and fastened to 
the work spindle sleeve on the other. This arm is rocked 
by a cam mechanism and slotted Unk at side opposite that 
shown in illustration. 




o 

a 

'-(-3 
u 

o 

a 
<v 
O 

> 

PQ 

C! 
o 

(33 

o 



GO 

o 
6 

1— I 



The cycle of operation is as follows: The machine 
being adjusted properly in its prehminary position, the 
tool shde and the head on which it is mounted are swung 
back about the vertical axis so that the tools clear the 



296 GEAR-CUTTING MACHINERY. 

work. The blank being set in the proper position, a cam 
movement swings the cutter shcle head inward until the 
tools reach the proper depth. The cam movement first 
mentioned now rocks upward the semicircular arm extend- 
ing around the back of the machine, rolhng the blank 
and (through the segmental crown and master gears) the 
slide, until the tools have been rolled out of contact in 
one direction, partially forming the teeth as they do so. 
The arm is then rolled back to the central position and 
along downward to the lower position, until the tools are 
rolled out of contact with the tooth in this direction, com- 
pleting the forming of the proper shape as they do so. 
The cam then rocks the arm back to the central position, 
where the cutter-slide head is swung back to clear the 
tooth, and the work is indexed, after which this cycle of 
operations is continued for the next tooth. It will be seen 
that by starting from the central position, going to each 
extreme and returning, all parts of each tooth are passed 
over twice, giving a roughing and a finishing chip. 

The machine is entirely automatic. The use of two 
tools presents a number of advantages. Not only does it 
increase the rate of working, but it balances the thrust of 
the cutting action of the two sides of the teeth and re- 
duces chatter and vibration, thus giving greater accuracy. 
The slides of each of the two tools, of course, have to be 
relatively adjusted to each other, depending on the pitch 
and number of the teeth being cut. 

Milling the Teeth of Bevel Gears on the Molding- 
Generating Principle. 

One of the most interesting and ingenious of all the 
machines for cutting the teeth of bevel gears is that shown 
in Fig. 209. It operates on the principle shown in Fig. 
165, in which the sides of the crown teeth are represented 



FORMING THE TEETH OF BEVEL GEARS. 297 

by the plane faces of milling cutters. In this machine the 
mining cutters and the imaginary crown gear remain sta- 
tionary so far as position is concerned, though, of course, 
the cutters revolve about their own axes. The work is 




Fig. 209. Brown & Sharpe Bevel Gear Generating Machine, cutting the 
Teeth by the use of Interlocking Milling Cutters of Large Diameter. 

held in the spindle of a head (resembling the universal 
head of the milling machine) which is mounted on the 
slide of a swinging sector at the left, which sector is 
rocked about a horizontal pivot in line with the axis of 
the imaginary crown gear. The work spindle and the 



298 GEAR-CUTTIXG MACHINERY. 

rocking movement of this sector are so connected by 
change gearing that, as the latter is oscillated through a 
sufficient angle to generate the teeth, the work is rolled in 
the proper ratio to mesh with the imaginary crown gear, 
a tooth of which is represented by the milling cutters. 
This movement is thus seen to be identical with that 
modification of the case in Fig. 164, in which the crown gear 
is stationary, while the frame is rocked, rolling the master 
gear on the crown gear and the work over the tool. 

The cutters used are of large diameter in proportion to 
the work for which the machine is intended, in order to 
minimize the deepening of the tooth space at the center 
which is characteristic of a gear cut in this way, as was 
explained in connection with Fig. 165. It will be seen 
that the teeth of the two milling cutters are set so as to 
interlock. In this way comparatively stiff cutting blades 
may be made to represent a complete crown gear tooth of 
very fine pitch. 

The machine is universally adjustable within its range. 
The cutter spindles may be set to give teeth of greater or 
smaller pitch, and to work with gears of large or small 
pitch cone radius. They may also be adjusted for teeth 
of greater or less angularity than the 14J-degree standard 
involute generally used. As in previous cases, it is not 
practicable to give here the details of the mechanism of 
this interesting machine. 

In Figs. 210 and 211 are shown views of two sides of the 
Warren bevel gear generating machine, first developed and 
built, if the writer's memory serves him, by the Pratt & 
Whitney Company, of Hartford, for the manufacture of 
chainless bicycle gears. The machine we show, however, 
is a design built for general manufacturing use by Ludwig 
Loewe & Co., of Berlin, Germany. This machine is approxi- 
mately similar in its action to the one built by Brown & 



FORMING THE TEETH OF BEVEL GEARS. 299 

Sharpe and just described. Aside from the differences in 
the mechanism, however, there are two important differ- 
ences in its action. One is the fact that the two cutters do 




Fig. 210. The Warren Bevel Gear Generating Machine as built by 
Ludwig Loewe & Co., Berlin. 

not cut on opposite sides of the same tooth space but on 
facing sides of alternate teeth, leaving a whole tooth 
untouched between them. The independent slides in 
which they are set are so arranged as to allow the plane 



300 



GEAR-CUTTING MACHIXERY. 



cutting face of the cutters to be set to agree with thje cor- 
responding faces of the imaginary crown gear. The other 
difference is the means taken to cut a tooth space having 
a straight bottom with cutters of small diameter. This is 
done by making the rolling of the cutter holder and the 
blank on each other a continuous rocking movement at 
a quite rapid rate. During this rapid rocking the cutter 
shdes are fed inward on their respective guides to form the 



rs- 




Fig. 211. The Working Side of the Warren Machine showing the 
Milhng Cutters, whose Plane Surfaces represent Sides of Adjacent 
Crown Gear Teeth. 

sides of the particular teeth at that time presented to 
the cutters. 

The cutter slides and guides are mounted on a circular 
head, which is rocked about the axis of the imaginary crown 
gear by the slotted crank and Hnk seen at the side of the 
machine in Fig. 211. The upper end of this circular slide 
carries a segment of a crown gear which meshes with the 
corresponding segment of a master gear on the work spindle, 
this arrangement being very similar to that of the Gleason 
machine shown in Fig. 208. The work and the cutters 



FORMING THE TEETH OF BEVEL GEARS. 301 

being rapidly rocked about each other while the cutters are 
slowly fed down through the tooth spaces, the sides of the 
teeth exposed to the action of the cutters are properly 
formed to the theoretical tooth curves. 

The construction of this machine is very ingenious, with 
provision for automatically effecting all the movements for 
rocking the cutter slides and the blank, feeding downward 
and returning, indexing, etc., with suitable adjustments for 
cutting gears of all kinds within the range of the machine. 

Bevel Gear Cutting Machines using a Hob and Oper- 
ating ON THE Molding-Generating Principle. 

While the bobbing principle is easily and simply applied 
to the cutting of spur and spiral gears, as illustrated in Figs. 
56 and 115, it requires but little thought to show that the 
apphcation of the same principle to the cutting of bevel 
gears is a difhcult if not hopeless task. Nevertheless, this 
problem has been attacked in two different directions. The 
principle of the mechanism and tools employed, however, 
requires to be studied with greater care than in the case of 
any of the machines we have previously described, if the 
reader is to have a clear understanding of their method of 
operation. The first of the two processes is that developed 
by M. Chambon, of Lyons, France. The operation of the 
machine is dependent on the principle of a pecuhar hob, 
whose generation and finished form are illustrated in Figs. 
212 to 216, inclusive. 

In Fig. 212 is shown the basic principle of the molding- 
generating process applied to the cutting of bevel gears, 
identical in its essentials with the mechanism shown in Fig. 
161, with the exception of the fact that a hob is used as a 
cutting tool instead of a reciprocating planer tool. At the 
left of the engraving a face view of the crown gear is shown. 



302 



GEAR-CUTTING MACHINERY. 



The width of the top of the tooth at the outside diameter is 
W, at the inner end of the tooth w. A hob may be made, 
such as No. 1, having teeth whose shape on a normal section 
EF exactly matches the same section of a tooth of the crown 
wheel when the teeth of both are centered on line CD and 
the hob is set at the helix angle d. Under these circum- 
stances a tooth of the hob would have a width W at the 
top. If the hob is single-threaded, and the crown gear has, 



" >1j ZI'-^-^ r 



HOB NO, 1 




SECTION ON C-D 



Fig. 212. Diagram showing the PossibiHty of Representing a Crown 
Gear Tooth by Teeth in a Series of Hobs of the Same Pitch Diameter 
but of Varying Lead and Helix Angle. 



for instance, twenty-four teeth, the two may be revolved 
together, the hob making twenty-four revolutions to one 
of the crown gear. Then this tooth of the hob, which 
comes into action at the time it is central with line CD, will 
exactly match the outline at the larger end of each of the 
teeth of the crown gear in turn, as it revolves. To have a 
hob which would similarly match the teeth at the smaller 
or inner end, we could construct one of the same diameter 
and of smaller pitch, smaller helix angle 6^, and a smaller 



FORMING THE TEETH OF BEVEL GEARS. 303 

width of flat, w, at the top of the tooth, all to correspond 
with the shape of the inner end of the crown gear tooth. It 
also should revolve in the ratio of 24 to 1 with the crown 
gear, and the tooth which comes central with the line CD at 
each revolution may be made to match accurately with the 
outhne of the inner end of the tooth. In the same way 
hobs may be made to be used at any intermediate point in 
the length of the tooth of the crown gear, so that one of the 
cutting edges will match the outline of the tooth at this 
point, once for every revolution of the hob. The problem 



HOB NO. 1 




Fig. 213. Comparison of the Hobs representing the Large and Small 
Ends of the Crown Gear Tooth in Fig. 212. 



is to construct a single hob which will do the work of hobs 
No. 1 and No. 2 and of all possible intermediate hobs 
between the two positions. 

In Fig. 213 the two hobs of Fig. 212 are shown enlarged. 
As previously explained, they are of the same diameter, with 
the normal width at the top of the teeth W and w, the same 
as that of the large and the small ends of the tooth of the 
crown gear, and with the leads of each, P and p, of the size 
required by the pitch of the large and small ends of the 
teeth. This gives corresponding angles d and d^ in the two 
cases. At T and V are shown axial sections of the thread 
for hobs Nos. 1 and 2. Since T and V correspond to the 



30-i 



GEAR-CUTTING MACHINERY. 



large and small ends of the teeth of a crown gear, the widths 
W^ and w^ are proportional to the leads P and p, and the 
angle of inclination of the sides, £, is the same in each case. 
What we have to do now is to combine Nos. 1 and 2 into a 
third which will do the work of both of the previous ones. 
Suppose we take a blank of the same diameter as the two 
hobs in Fig. 213 and thread it first with the same shape and 
pitch of thread as for No. 1, and second with the same pitch 
and shape as for No. 2, except that while the width of the 
top and the inclination of the sides remain the same, the 
cut will be carried to the full depth required for the thread 



Fr--.. 



__ . _ DEVELOPED CIRCUm|fERENCE.OF HOB 

B 




Fig. 214. Development of the Thread of a Hob of the Same Diameter 
as in Fig. 213, in which have been cut the Two Threads of the Two 
Hobs there shown. 



of No. 1. As shown at U in Fig. 213, the dotted section of 
No. 2 is the same as for V, except for its increased depth. 
When the hob has been thus threaded the developed cir- 
cumference at the point where the tops of the two threads 
cross each other will be shown in Fig. 214. Here lines FC 
and AH represent the top of thread No. 1, inclined at the 
threading angle d as determined by the pitch, while the 
space included between lines AG and EC correspondingly 
represents the top surface of thread No. 2, incHned at angle 
d\ These two threads have widths at the top of W and w, 
proportional to the pitch as before. The center hues of the 



FORMING THE TEETH OF BEVEL GEARS. 305 

tops of the two threads cut in the blank cross each other at 
point 0. The top of the thread is seen to be cut in a par- 
allelogram ABCD, this being the metal left after the grooves 
for the two different threads have been cut. Axial sections 
of this remaining fragment of the thread are shown on lines 
FN, QD, BT, and CH; as may be seen, the incHnation of 
the sides of the thread, as measured on an axial section at 
each of these points (and at all other points as well), is 
made e. 

A short hob, threaded as in Fig. 214, is shown in Fig. 215. 
Similar points in each figure have similar letters. Since 




Fig. 215. Hob (ungashed) produced by combining the 
Two shown in Fig. 213; the Thread is the same 
as that shown Developed in Fig. 214:. 

the two sides of the teeth, which unite in point B, have the 
same inclination as measured on a plane passing through the 
axis of the hob, their intersection will also have the same 
inclination, and the line of intersection will pass through the 
axis of the hob. The same is true of point D on the other 
side of the thread. If the hob is gashed at B and D, the 
cutting edges thus formed are evidently common to both 
the large thread of width W and angle 6 and the small 
thread of width w and angle d\ and when properly set in the 
machine and rotated with the crown gear the relation to 
the imaginary crown gear will correspond exactly to that 



306 GEAR-CUTTING MACHINERY. 

gear in the position of either hob No. 1 or No. 2 in Fig. 212, 
the same hob thus taking the place of both. 

It next remains to be shown that these two cutting edges 
at B and D in Fig. 215 can be made to correspond with all 
the sections of the crown gear intermediate between the 
large and the small ends in Fig. 212. 

To prove this, we have to show that the sides of any 
thread cut in this hob with a center line passing through 
0, whose width of top and lead are in the same proportion 
as in Fig. 213, and whose sides have the same inclination 
as measured on an axial plane, will include the cutting 
edges B and D, which we have formed as described in the 
hob in Fig. 215. In Fig. 214 any thread of the given pro- 
portions, such as FCAH, will cut the horizontal line NR 
at D, in such a way that OD:OS = DP: KS. Now DP 
is half the width of the tooth on the axial section, and KS 
is half the circumferential pitch, so that OD : OS = 

Tf' P 

— : - = TF' : P. But all the threads we are concerned 

with have the same ratio between W and P, so that the 
sides of all of them cross line RS at D. The same thing 
applies to the crossing at B on the upper side. The cut- 
ting edges, then, at D and B are common to all the hobs 
of the same diameter which will fill the required condition 
for the infinite number of sections between hobs Nos. 1 
and 2 in Fig. 212. 

In practice, the hob of Fig. 215, made as we have 
described, is gashed throughout the full length of the 
thread, as well as at the cutting edges B and D. Such a 
hob is shown in two positions in Fig. 216. The edges B 
and Z), however, are the ones which are relied on to give 
the true shape to the teeth of the gear. 

The next problem, and a somewhat complicated one, is 
that of providing a machine which will utihze this hob, in 



FORMING THE TEETH OF BEVEL GEARS. BOT 

accordance with the principles of its construction, to take 
the place of the imaginary crown g(\ar of Fig. 212 in gen- 
erating teeth in a bevel gear blank. In the first place, 
the hob must be moved from the position occupied by No. 1 
to that occupied by No. 2, changing its angle continuously 
meanwhile from to 0' to agree with the change in helix 
angle due to the change of pitch as the tooth grows smaller. 
Next, the hob and the blank being cut must be rotated 
with each other, so that the hob revolves during one 
revolution of the gear as many times as there are teeth in 
the latter, the hob being supposed to be single- threaded. 





Fig. 216. The Completed Hobs used in the Chambon Machine, 
developed as shown in the Preceding Illustrations. 

These two conditions are easily fulfilled, but there still 
remains a third. The two cutting edges we have made 
for the hob represent the sides of each tooth of the imagi- 
nary crown gear only when each tooth in turn is passing 
the center line CD. In order to have a generating action 
on the blank, the imaginary teeth of the crown gear must 
have a cutting action over a considerable angle about Z), 
on both sides of the section CD. This may be effected by 
rocking the holder which carries the hob about center D 
in either direction, meanwhile rotating the hob to keep 
its thread in the proper relation with the teeth of the 
crown gear, as if the latter was stationary. In the ma- 
chine this oscillation of the hob and its carrier about D, 



308 GEAR-CUTTING MACHINERY. 

on each side of CD, takes place continuously, while the 
hob is being fed down from the position occupied by 
No. 1 to that of No. 2, and the rotation of the hob re- 
quired by this oscillation (to keep the hob and the crown 
gear continuously in step) is superimposed on the other 
rotation in unison with the imaginary crown gear and 
the work, the two being combined by differential gearing 
of the same style as required for combining the move- 
ments in spiral gear cutting machines as illustrated in 
Fig. IIG. When this is done, a cutting edge will be pro- 
vided by the hob closely paralleling the molding action 
of the crown gear as shown at the right of Fig. 212. 

The machine for accomplishing all this is shown in Fig. 
217. The work is mounted on an arbor adjustable to 
any angle and to any axial position in relation to the hob. 
The spindle for the latter is mounted in a swinging car- 
rier which slides on ways provided on the face of a head, 
which latter is oscillated about a horizontal axis. A suit- 
able compensating movement is provided, so that this 
rocking movement is translated into the required rotary 
motion of the cutter, as was shown, to keep it from getting 
out of step with the imaginary crown gear, and for com- 
bining it properly with the constant rotation of the cutter 
derived from its connection with the work-revolving 
mechanism. The spindle carrier feeds in along the ways 
of the oscillating head, being swung around by a templet 
as it proceeds, to change the helix angle 6 as required. 
Suitable change gears are provided for all the movements, 
and one passing through of the continuously rotating hob 
finishes the gear complete. The mechanism is rather too 
intricate to describe here in detail. A number of compen- 
sating movements are required, which add somewhat to 
its complexity. 

We should not leave the discussion of this machine and 



FORMING THE TEETH OF BEVEL GEARS. 309 



its principle, ingenious though it is, without noting that 
the process involves a number of minor inaccuracies. 
For one thing, an error is introduced by the fact that in 
the machine the rocking of the spindle-head carrying the 
hob is about the axis X^Y', instead of about axis XY, as 
it should be. (See Fig. 212.) This is doubtless done to 




>^<xi^ 



Fig. 217. The Chambon Continuous Bevel Gear Robbing Machine, 
employing the Cutters shown in Fig. 216. 



avoid the complication of having to set the machine for 
the angle of the top of the crown tooth. The error intro- 
duced would be entirely negligible except, perhaps, in the 
case of gears very closely approaching crown gears in their 
pitch cone angle. There are several other little discrep- 
ancies which, however, are scarcely worth taking into 



310 



GEAR-CUTTING MACHINERY. 



account. This process and machine are the invention ot 
M. Chambon, of Lyons, France. 

In Fig. 218 is shown another machine operating on the 
Chambon plan, built by the Societe Suisse pour la Con- 
struction des Machines-Outils Oerhkon, Oerlikon pres 
Zurich, Switzerland. This machine employs the cutter 




Fig. 218. The Cham])on Bevel Gear Hobbing Machine as developed by 
the Oerlikon Company, particularly adapted for roughing Bevel 
Gears preliminary to planing. 



in Fig. 21(), but the mechanism is very much simpler, 
since the oscillating head and the connections required for 
operating it have been abandoned, the spindle slide being 
mounted directly on fixed ways on the front of the col- 
umn. For this reason the generating action is not, it will 
be seen, fully carried out, the cutting action, however, 
resulting in the production of a groove tapering properly 



FORMING THE TEETH OF BEVEL GEARS. 311 



from the large to the small end and of approximately the 
correct shape. The machine is thus especially adapted to 
roughing blanks previous to finishing them in a planing 
machine operating on the templet or molding-generating 
principles. It is claimed to do its work with great rapid- 
ity, and to be capable of leaving a very small and uniform 
amount of stock over the whole area of the sides of the 
tooth. 
Besides this Chambon process, another and, it seems to 



1st position) / 



J; JaND POSITION 

^; r ( OF HOB 




SECTION ON C-D 

Fig. 219. Another Hobl^ing Process suggested for Bevel Gears. 



the writer, a fruitless attempt has been made to cut the 
teeth of bevel gears by the molding-generating principle 
with a hob as the cutting tool. This method is shown in 
its principle in Fig. 219, the construction being referred to 
the imaginary crown gear and the bevel gear to be cut, as 
in the previous case. Also, as in the previous case, the 
action hinges about the design of the hob. Here we have 
a hob of such a taper, and with the pitch continuously 
decreasing in such a ratio, that the helix angle is constant. 
This decrease in pitch is, of course, accompanied by a cor- 



312 GEAR-CUTTING MACHINERY. 

respondingiy uniform and proportional decrease in the 
section of the thread. In the machine the hob is so set 
(in the "first position/' for instance) that the center Hne 
of the thread in the cutting position passes through cen- 
ter D of the imaginary crown gear. Here the width of the 
top of the hob tooth is W , corresponding to the desired 
width at the top of the imaginary crown gear tooth. In 
feeding, the hob is moved, without changing the angle of 
its axis, along line EF, so that when it arrives at the 
inner end of the face of the imaginary crown gear, that 
tooth that is on the center line CD will be so near the 
small end of the hob that it has the required width at the 
top, 10, and the proper pitch, to agree with the small end 
of the tooth in the imaginary crown gear. In a similar 
way all the intervening positions match up with the 
teeth of the crown gear on line CD. 

In the machine for utihzing this hob it is mounted on 
a sHde which is adjustable to give the line of feed, EF, the 
angle for the concUtions required, while, as shown at the 
right of Fig. 214, the spindle of the hob is set at such an 
angle that its pitch cone is tangent to the pitch plane of 
the imaginary crown gear. The feeding movement along 
hne EF is so connected with the rotating mechanism of 
the hob that, as it progresses from the first to the second 
position, the hob is rotated to keep its diminishing thread 
always coincident with the central tooth of the crown 
gear shown. In addition to the rotation thus given the 
hob by the feeding movement, another rotating movement 
is given it in connection with the work, the same as for all 
bobbing processes. These two rotating movements are 
combined by differential gearing. It will thus be seen 
that with the machine properly set up the hob may be 
fed from the first to the second position, with the hob and 
work rotating together, the former being under a rotative 



FORMING THE TEETH OF BEVEL GEARS. 313 

influence from the feeding movement as well, giving some- 
what the effect of the rotation of the ordinary crowTi gear. 
^Yh.Sit the writer feels sure, however, is a vital error in 
the principle of this machine, is plainly evident in Fig. 219, 
where it is seen that the only point where the teeth of the 
hob coincide with those of the imaginary crown gear is on 
line CD. At the right of CD and at the left of it the 
coincidence ceases, and the hob teeth cross the crown gear 
teeth at different angles, so that they must cut entirely 
different shaped spaces in the work. Of course, every- 
thing in the diagram shown is exaggerated, but the 
exaggeration only shows the principle more clearly. While 
it is stated that the machine and the process are beyond 
the experimental stage, and while, from long experience^ 
the writer knows that it is unsafe to predict the failure 
of any principle until it has actually been tried out, the 
analysis given above is surely enough to make one skeptical 
as to the success of this operation, particularly in the case 
of gears of such large pitch cone angle as to nearly approach 
the crown gear. With smaller angles, down to the spur 
gear, the action should be more nearly correct, as the blank 
curves away from the hob so rapidly as to avoid most of 
the interference, though even here the fact that the pitch 
is coarser at one side of the line CD than at the other would 
still prevent proper action. It would thus seem that inter- 
ference would prevent the consideration of this device as a 
practical possibility. 

Comparison of Molding-Generating Machines 
FOR Bevel Gears. 

It is interesting to note, in the various molding-generating 
machines for bevel gears, the different ways used for rolling 
the cutter head and the work in relation to each other. In 
the Bilgram machine the proper relation is maintained by the 



314 GEAR-CUTTING MACHINERY. 

rolling of the pitch surfaces of the work and the crown 
gear on each other, the rolling being controlled by steel 
tapes or wires in such a way as to make the movement 
positive. In the Ducommun machine the same movement 
is effected by spherical linkage, which, while not exact in 
its action, is so nearly so that the error introduced is 
entirely negligible. The Gleason and Ludwig Loewe machines 
employ segments of the actual crown and master gears 
shown in Fig. 164, although, of course, it is not necessary 
to have the teeth of the master gear of the same number 
for the full circle and of the same form as those of the work, 
the only requirement being that the pitch cone of the 
master gear be coincident with that of the work. In the 
Ernault machine the proper ratio of movement is obtained 
by a system of angular slides which automatically adjust 
themselves to the required ratio (which is dependent on 
the pitch cone angle of the gear) in the manner described in 
referring to Fig. 207. Finally, in the Brown & Sharpe, 
Chambon, and Churchill machines the proper ratio is 
obtained by the use of change gears. 

Another interesting point relates to the considerable 
size and complication of each of these machines, as com- 
pared with the small size of the work they are adapted to 
operate on. While the principle of the molding-generating 
process is comparatively simple, as shown in Fig. 164, 
considerable mechanism is required for making a machine 
built according to this principle universal in its application, 
easily set up and operated, and automatic in its operation. 

Conclusion. 

This concludes our investigation of gear-cutting machin- 
ery. The number of commercial machines of this kind 
is much greater than was believed possible when the 
author began these chapters. It is safe to say that in no 



FORMING THE TEETH OF BEVEL GEARS. 316 

other field of the machine tool business has there been 
such an opportunity for the display of mechanical ingenuity 
and skill in designing as in that of gear cutting, and in 
no field have these possibilities been so fully grasped. 
That we have not yet reached final development in any 
of the various forms of this machinery is shown by the 
fact that a number of new machines are in process of 
development in this country and Europe, and doubtless 
such as are worthy of mention will be brought to the atten- 
tion of the readers of the technical press as soon as the 
information concerning them is available for publication. 



INDEX. 



Act-Ges. f iir Schmirgel u, Maschinen-Fabrikation 242 

Adams Company 87 

Armstrong, Sir W. G., Whitworth & Co 48, 50, 93, 107, 126 

Ateliers de Construction Mecaniques, ci-devant Ducommun . 83, 281, 314 

Atlas, Nya Aktiebolaget 51, 106, 142, 202, 208 

Automatic Machine Company 135 

Becker Milling Machine Company 33, 82 

Biernatzki & Co 163 

Bilgram, Hugo 69, 157, 274, 278, 281, 313 

Bouhey, Usines 250, 254, 274, 291 

Brown, David, & Sons 110 

Brown & Sharpe Manufacturing Company. . . . 26, 33, 112, 137, 236, 

240, 275, 297, 298, 314 

Browning 259 

Burton, C. W., Griffiths & Co 90, 102 

Chambon, M 301, 310, 314 

Chouanard, E 102 

Churchill Machine Tool Company 290, 314 

Cincinnati Gear Cutting Machine Company 36 

Cincinnati Milling Machine Company 20, 139, 232 

Citroen, Andre 151 

Craven Brothers 55, 1 18 

Darling & Sellers 52 

Dubosc, Officina Meccanica Ing. E 267 

Ducommun (ci-devant) Ateliers de Construction Mecaniques. . 83, 147 

281, 314 

Ernault, H 290, 314 

Fellows Gear Shaper Company 75, 99, 100, 108, 126, 128, 155 

Flather, E. J., Manufacturing Company 37, 238 

Garvin Machine Company , 201 

Gildemeister & Co 87, 147 

317 



318 INDEX. 

Gleason Works 15, 66, 248, 295, 800, 314 

CJould & Eberhardt. . . . 38, 56, 105, 114, 120, 130, 152, 164, 193, 237 

Grant-Lees Machine Company 171, 195 

Greenwood & Batley 254 

Hardinge Brothers 60 

Herbert, Alfred 92 

Hetherington, John, & Sons 48, 58 

Holroyd & Co 166, 209 

Ilumpage, Thomas 102 

Humpage, Thompson & Hardy 88 

Juengst, Geo., & Sons 173 

Junghans, Wilhelm, Werkzei-gmaschinenfabrik 84 

Kroll, Moritz 246 

Le Blond, R. K., Machine Tool Company. . 21, 81, 112, 118, 141, 189 

Le Jeun, Etablissements Marcel 235 

Loewe, Ludwig, & Co 22, 42, 233, 298, 314 

Lorenz, Maschinenfabrik 95, 147 

Mill, Fred 243 

Monneret, M 290 

Newark Gear Cutting Machine Company 24, 36, 59, 192, 206, 240 

Newton Machine Tool Works 15, 53, 67, 169, 190 

Oerlikon, Societe Suisse pour la Construction de Machines-Outils, 

256, 266, 310 

Parkinson, J. & Son 42 

Pederson , 16 

Pfauter 171 

Pratt & Whitney Company 14, 58, 118, 148, 176, 298 

Reinecker, J. E 44, 81, 99, 102, 121, 143, 150, 178, 

200, 211, 281, 292 
Reynolds Machine Company 98 

Rhenania 90, 180 

Rice 261 

Schubert & Salzer Maschinenfabrik 46, 90 

Schuchardt & Schutte 171 

Schutte, Alfred 90 



INDEX. 319 

Slate, Dwight, Machine Company , 29, 60 

Sloan & Chace Maniifacturino; Company 29, 00, 62, 114 

Small Arms & Machine Factory Company 257 

Smith, G. F 58 

Smith & Coventry 271 

Societe Frangaise de Machines-Outils 72 

Sonnenthal, Selig, & Co 90, 271 

Spencer & Spiers 73 

Standard Manufacturing Company , 02 

Swasey, Ambrose 14 

Upton & Oilman 65 

Vickers Sons and Maxim 19 

Walcott & Wood Machine Tool Company 115, 126 

Wallwork, Henry, & Co 92, ISO, 211 

Waltham Machine Works 64 

Wanderer Fahrradwerke 86, 189 

Warner & Swasey 98, 1 17 

Warren 298 

Whiton, D. E., Machine Company 239 

Wilkinson, G., & Son . 46, 123 

Wiist, C. E., & Co. , 179 



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* Dyer's Handbook of Light Artillery i2mo, 

Eissler's Modern High Explosives 8vo, 

* Fiebeger's Text-book on Field Fortification.. Large i2mo, 

Hamilton and Bond's The Gunner's Catechism i8mo, 

* Hofif's Elementary Naval Tactics 8vo, 

Ingalls's Handbook of Problems in Direct Fire. Svo, 

* Lissak's Ordnance and Gunnery Svo, 

* Ludlow's Logarithmic and Trigonometric Tables Svo, 

* Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and II.. Svo, each, 

* Mahan's Permanent Fortifications. (Mercur) Svo, half mor. 

Manual for Courts-martial i6mo, mor. 

* Mercur's Attack of Fortified Places i2mo, 

* Elements of the Art of War Svo, 

Metcalf's Cost of Manufactures — And the Administration of Workshops. .Svo, 

Nixon's Adjutants' Manual 24mo, 

Peabody's Naval Architecture. Svo, 

* Phelps's Practical Marine Surveying Svo, 

Putnam's Nautical Charts Svo, 

Sharpe's Art of Subsisting Armies in War iSmo, mor. 

* Tupes and Poole's Manual of Bayonet Exercises and Musketry Fencing. 

24mo, leather, 

* Weaver's Military Explosives ^ Svo, 

Woodhull's Notes on Military Hygiene i6mo, 



ASSAYING. 

Betts's Lead Refining by Electrolysis 8vo, 4 00 

Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. 

i6mo, mor. 

Furman's Manual of Practical Assaying Svo, 

Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. . . .Svo, 

Low's Technical Methods of Ore Analysis Svo, 

Miller's Cjanide Process i2mo. 

Manual of Assaying i2mo, 

Minet's Production of Aluminum and its Industrial Use. (Waldo)..". . . . i2mo, 

O'Driscoli's Notes on the Treatment of Gold Ores Svo, 

Ricketts and Miller's Notes on Assaying Svo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc) Svo, 

Ulke's Modern Electrolytic Copper Refining Svo, 

Wilson's Chlorination Process i2mo. 

Cyanide Processes i2mai 



ASTRONOMY. 

Comstock's Field Astronomy for Engineers Svo, 

Craig's Azimuth 4to, 

Crandall's Text-book on Geodesy and Least Squares Svo, 

Doolittle's Treatise on Practical Astronomy Svo, 

Gore's Elements of Geodesy Svo, 

Ha3rford's Text-book of Geodetic Astronomy Svo, 

Merriman's Elements of Precise Surveying and Geodesy Svo, 

* Michie and Harlow's Practical Astronomy Svo, 

Rust's Ex-meridian Altitude, Azim^ith and Star-Finding Tables Svo, 

* White's Elements of Theoretical and Descriptive Astronomy i2mo, 

3 



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CHEMISTRY. 

* Abderhalden's Physiological Chemistry in Thirty Lectures. (Hall and Defren) 

8vo, 5 oo 

* Abegg's Theory of Electrolytic Dissociation, (von Ende) i2mo, i 25 

Alexeyeff's General Principles of Organic Syntheses. (Matthews) 8vo, 3 00 

Allen's Tables for Iron Analysis 8vo, 3 00 

Arnold's Compendium of Chemistry. (Mandel) Large i2mo, 3 50 

Association of State and National Food and Dairy Departments, Hartford, 

Meeting, 1906 8vo, 3 00 

Jamestown Meeting, 1907 8vo, 3 00 

Austen's Notes for Chemical Students i2mo, i 50 

Baskerville's Chemical EJements. (In Preparation.) 

Bemadou's Smokeless Powder. — Nitro-cellulose, and Theory of the Cellulose 

Molecule i2mo5 2 50 

Bilts's Chemical Preparations. (Hall and Blaachard). (In Press.) 

♦Blanchard's Synthetic Inorganic Chemistry i2mo, i 00 

* Browning's Introduction to the Rarer Elements 8vo, i 50 

Brush and Penfield's Manual of Determinative Mineralogy 8vo, 4 00 

* Claassen's Beet-sugar Manufacture. (Hall and Rolfe) 8vo, 3 00 

Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood). . .8vo, 3 00 

Cohn's Indicators and Test-papers i2mo, 2 00 

Tests and Reagents 8vo, 3 00 

* Danneel's Electrochemistry. (Merriam) i2mo, i 25 

Dannerth's Methods of Textile Chemistry i2mo, 2 00 

Duhem's Thermodynamics and Chemistry. (Burgess) 8vo, 4 00 

Eakle's Mineral Tables for the Determination of Minerals by their Physical 

Properties 8vo, 1 25 

Eissler's Modern High Explosives 8vo, 4 00 

EfTront's Enzymes and their Applications. (Prescott) 8vo, 3 00 

Erdmann's Introduction to Chemical Preparations. (Dunlap) i2mo, i 25 

* Fischer's Physiology of Alimentation Large i2mo, 2 00 

Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. 

i2mo, mor. i 50 

Fowler's Sewage Works Analyses i2mo, 2 00 

Fresenius's Manual of Qualitative Chemical Analysis. (Wells). Svo, 5 00 

Manual of Qualitative Chemical Analysis. Part I. Descriptive. (Wells) Svo, 3 00 

Quantitative Chemical Analysis. (Cohn) 2 vols Svo, 12 50 

When Sold Separately, Vol. I, $6. Vol. II, $8. 

Fuertes's Water and Public Health i2mo, i 50 

Furman's Manual of Practical Assaying Svo, 3 00 

* Getman's Exercises in Physical Chemistry i2mo, 2 00 

GiU's Gas and Fuel Analysis for Engineers i2mo, i 25 

* Gooch and Browning's Outlines of Qualitative Chemical Analysis. 

Large i2mo, i 25 

Grotenfelt's Principles of Modern Dairy Practice. (WoU) i2mo, 2 00 

Groth's Introduction to Chero'':al Crystallography (Marshall) i2mo, i 25 

Hammarsten's Text-book of Physiological Chemistry. (Mandel) Svo, 4 00 

Hanausek's Microscopy of Technical Products. (Winton) 8vo, 5 00 

* Haskins and Macleod's Organic Chemistry . i2mo, 2 00 

Helm's Principles of Mathematical Chemistry, (Morgan) i2mo, i 50 

Bering's Ready Reference Tables (Conversion Factors) i6mo, mor. 2 50 

* Herrick's Denatured or Industrial Alcohol Svo, 4 00 

Hinds's Inorganic Chemistry 8vo, 3 00 

* Laboratory Manual for Students i2mo, i 00 

* Holleman's Laboratory Manual of Organic Chemistry for Beginners. 

(Walker^ i2mo, 1 00 

Text-book of Inorganic Chemistry, (Cooper). Svo, 2 50 

Text-book of Organic Chemistry. (Walker end Mott). ......,» Svo, 2 50 

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olley and Ladd's Analysis of Mixed Paints, Color Pigments , and Varnishes. 

Large i2mo, 

Hopkins's Oil-chemists' Handbook. 8vo, 

Iddings's Rock Minerals 8vo, 

Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo, 
Johannsen's Determination of Rock-forming Minerals in Thin Sections . .Svo, 
Johnson's Chemical Analysis of Special Steel. Steel-making. (Alloys and 
Graphite.) (In Press.) 

Keep's Cast Iron Svo, 

Ladd's Manual of Quantitative Chemical Analysis i2mo, 

Landauer's Spectrum Analysis. (Tingle) Svo, 

* L,angwortny and Austen's Occurrence of Aluminium in Vegetable Prod- 

ucts, Animal Products, and Natural Waters Svo, 

Lasszu-Cohn's Application of Some General Reactions to Investigations in 

Organic Chemistry. (Tingle) i2mo, 

Leach's Inspection and Analysis of Food with Special Reference to State 

Control Svo, 

Lob's Electrochemistry of Organic Compounds. (Lorenz) Svo, 

Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. .. .Svo, 

Low's Technical Method of Ore Analysis Svo, 

Lunge's Techno-chemical Analysis. (Cohn).. i2mo, 

* McKay and Larsen's Principles and Practice of Butter-making Svo, 

Maire's Modem Pigments and their Vehicles i2mo, 

Mandel's Handbook for Bio-chemical Laboratory i2mo, 

* Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe. . i2mo. 
Mason's Examination of Water. (Chemical and Bacteriological.). . . .i2mo. 

Water-supply. (Considered Principally from a Sanitary Standpoint. 

Svo, 
Mathewson's Chemical Theory for First Year College Students. (In Press). 
Matthews's Textile Fibres. 2d Edition, Rewritten Svo, 

* Meyer's Determination of Radicle? in Carbon Compounds. (Tingle). . i2mo. 
Miller's Cyanide Process i2mo. 

Manual of Assaying i2mo, 

Minet's Production of Aluminum and its Industrial Use. (Waldo) i2mo, 

Mixter's Elementary Text-book of Chemistry i2mo, 

Morgan's Elements of Physical Chemistry izmo. 

Outline of the Theory of Solutions and its Results i2mo, 

* Physical Chemistry for Electrical Engineers i2mo, 

Morse's Calculations used in Cane-sugar Factories i6mo, mor. 

* Muir's History of Chemical Theories and Laws Svo, 

MuUiken's General Method for the Identification of Pure Organic Compounds. 

Vol. I Large Svo, 

O'DriscoU's Notes on the Treatment of Gold Ores Svo, 

Ostwald's Conversations on Chemistry. Part One. (Ramsey) i2mo. 

Part Two. (Turnbull) i2mo, 

* Palmer's Practical Test Book of Chemistry i2mo, 

* Pauli's Physical Chemistry in the Service of Medicine. (Fischer") i2mo, 

* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 

Svo, paper, 50 
Tables of Minerals, Including the Use of Minerals and Statistics of 

Domestic Production 8vo, 

Pictet's Alkaloids and their Chemical Constitution. (Biddle) Svo, 

Poole's Calorific Power of Fuels 8vo, 

Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- 
ence to Sanitary Water Analysis i2mo, 

* Reisig's Guide to Piece-dyeing 8vo, 

Richards and Woodman's Air, Water, and Food from a Sanitary Standpoint.. 8 vo, 

Ricketts and Miller's Notes on Assaying 8vo 

Rideal's Disinfection and the Preservation of Food Svo, 

Sewage and the Bacterial Purification of Sewage Svo, 

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Riggs's Elementary Manual for the Chemical Laboratory 8vo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc) ,. . . .8vo, 

Ruddiman's Incompatibilities in Prescriptions 8vo, 

Whys in Pharmacy i2mo, 

Ruer's Elements of Metallography. (Mathewson) (In Preparation.) 

Sabin's Industrial and Artistic Technology of Paints and Varnish Svo, 

Salkowski's Physiological and Pathological Chemistry. (Orndorff) Svo, 

Schimpf's Essentials of Volumetric Analysis i2mo, 

* Qualitative Chemical Analysis Svo, 

Text-book of Volumetric Analysis i2mo. 

Smith's Lecture Notes on Chemistry for Dental Students Svo, 

Spencer's Handbook for Cane Sugar Manufacturers i6mo, mor. 

Handbook for Chemists of Beet-sugar Houses i6mo, mor. 

Stockbridge's Rocks and Soils Svo, 

* Tillman's Descriptive General Chemistry Svo, 

* Elementary Lessons in Heat .Svo, 

Treadwell's Qualitative Analysis. (Hall) Svo, 

Quantitative Analysis. (Hall) Svo, 

Turneaure and Russell's Public Water-supplies Svo, 

Van Deventer's Physical Chemistry for Beginners. (Boltwood) i2mo, 

Venable's Methods and Devices for Bacterial Treatment of Sewage Svo, 

Ward and Whipple's Freshwater Biology. (In Press.) 

Ware's Beet-sugar Manufacture and Refining. Vol. I Small Svo, 

V'^1. II SmallRvo, 

Washington's Manual of the Chemical Analysis of Rocks Svo, 

* Weaver's MXtary Explosives Svo, 

Wells's Laboratory Guide in Qualitative Chemical Analysis Svo, 

Short Course in Inorganic Qualitative Chemical Analysis for Engineering 
Students i2mo. 

Text-book of Chemical Arithmetic i2mo, 

Whipple's Microscopy of Drinking-water Svo, 

Wilson's Chlorination Process i2mo, 

Cyanide Processes i2mo, 

Winton's Microscopy of Vegetable Foods Svo, 

CIVIL ENGINEERING. 

BRIDGES AND ROOFS. HYDRAULICS. MATERIALS OF ENGINEER- 
ING. RAILWAY ENGINEERING. 

Baker's Engineers' Surveying Instruments i2mo, 3 00 

Bixby's Graphical Computing Table Paper ig*^ ^■^ 24! inches. 25 

Breed and Hosmer's Princioles and Practice or Surveying. 2 Volumes. 

Vol. I. Elementary Surveying •. Svo, 3 00 

Vol. II. Higher Surveying Svo, 2 50 

* Burr's Ancient and Modern Engineering and the Isthmian Canal .... Svo, 3 50 
Comstock's Field Astronomy for Engineers Svo, 2 50 

* Corthell's Allowable Pressures on Deep Foundations i2mo, i 25 

Crandall's Text-book on Geodesy and Least Squares Svo, 3 00 

Davis's Elevation and Stadia Tables Svo, i 00 

Elliott's Engineering for Land Drainage i2mo, i 50 

Practical Farm Drainage i2mo, 00 

*Fiebeger's Treatise on Civil Engineering Svo, 5 00 

Flemer's Phototopographic Methods and Instruments Svo, 5 00 

Folwell's Sewerage. (Designing and Maintenance.) Svo, 3 00 

Freitag's Architectural Engineering Svo, 3 50 

French and Ives's Stereotomy Svo, 2 50 

Goodhue's Municipal Improvements i2mo, i 50 

Gore's Elements of Geodesy 8vo, 2 50 

* Hauch's and Rice's Tables of Quantities for Preliminary Estimates . . T2mo, i 25 

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Hayford's Text-book of Geodetic Astronomy 8vo, 

Hering's Ready Reference Tables. (Conversion Factors) i6mo, mor. 

Howe's Retaining Walls for Earth i2mo, 

* Ives's Adjustments of the Engineer's Transit and Level i6mo, Bds. 

Ives and Hilts's Problems in Surveying i6mo, mor. 

Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 

Johnson's (L. J.) Statics by Algebraic and Graphic J\Iethods 8vo, 

Kinnicutt, Winslow and Pratt's Purification of Sewage. (In Preparation.) 
Laplace's Philosophical Essay on Probabilities. (Truscott and Emory) 

i2mo, 
Mohan's Descriptive Geometry , 8vo, 

Treatise on Civil Engineering. (1S73.) (Wood) Svo, 

Merriman's Elements of Precise Surveying and Geodesy Svo, 

Merriman and Brooks''s Handbook for Sxirveyors i6mo, mor. 

Nugent's Plane Surveying Svo, 

Ogden's Sewer Construction Svo, 

Sewer Design , i amo, 

Parsons's Disposal of Municipal Refuse. ... Svo, 

Patton's Treatise on Civil Engineering. Svo, half leather. 

Reed's Topographical Drawing and Sketching 4to, 

Rideal's Sewage and the Bacterial Purification of Sewage Svo, 

Riemer's Shaft-sinking under Difficult Conditions. (Coming and Peele). . . Svo, 

Siebert and Biggin's Modern Stone-cutting and Masonry Svo, 

Smith's Manual of Topographical Drawing. (McMillan) Svo, 

Soper's Air and Ventilation of Subways Large i2mo, 

Tracy's Plane Surveying i6mo, mor. 

* Trautwine's Civil Engineer's Pocket-book i6mo, mor. 

Venable's Garbage Crematories in America Svo, 

Methods and Devices for Bacterial Treatment of Sewage .Svo, 

Wait's Engineering and Architectural Jurisprudence Svo, 

Sheep, 

Law of Contracts Svo, 

Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture Svo, 

Sheep, 
Warren's Stereotomy — Problems in Stone-cutting Svo, 

* Waterbury's Vest-Pocket Hand-book of Mat lematics for Engineers. 

2|X 5s inches, mor. i 00 
Webb's Problems in the Use and Adjustment of Engineering Instruments. 

i6mo, mor. i 25 

Wilson's (H. N.) Topographic Surveying Svo, 3 50 

Wilson's (W. L.) Elements of Railroad Track and Construction i2mo, 2 00 

BRIDGES AND ROOFS. 

Boiler's Practical Treatise on the Construction of Iron Highway Bridges. .Svo, 2 00 

Burr and Falk's Design and Construction of Metallic Bridges Svo. 5 00 

Influence Lines for Bridge and Roof Computations Svo, 3 00 

Du Bois's Mechanics of Engineering. Vol. II Sn:all 4to, 10 00 

Foster's Treatse on Wooden Trestle Bridges 4to, 5 00 

Fowler's Ordinary Foundations Svo, 

French and Ives's Stereotomy 8vo 

Greene's Arches in Wood, Iron, and Stone Svo, 

Br'dge Trusses Svo 

Roof Trusses Svo 

Grimm's Secondary Stresses in Bridge Trusses Svo, 

Heller's Stresses in Structures and the Accompanying Deformations Svo, 

Howe's Design of Simple Roof-trusses in Wood and Steel Svo, 

Symmetrical Masonry Arches. , Svo, 

Treatise on Arches Svo. 

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Johnson, Bryan, and Turneaure's Theory and I*ractice in the Designing of 

Modern Framed Structures Small 4to, lo oo 

Merriman and Jacoby's Text-book on Roofs and Bridges: 

Part I. Stresses in Simple Trusses 8vo, 

Part II. Graphic Statics 8vo, 

Part III. Bridge Design 8vo, 

Part IV. Higher Structures Svo, 

Morison's Memphis Bridge Oblong 4to, 

Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches. 

Svo, 

Waddell's De Pontibus, Pocket-book for Bridge Engineers i6mo, mor, 

* Specifications for Steel Bridges i2mo, 

Waddell and Harrington's Bridge Engineering. (In Preparation.) 

Wright's Designing of Draw-spans. Two parts in one volume Svo, 3 so 

HYDRAULICS. 

Barnes's Ice Formation Svo, 3 00 

Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from 

an Orifice. (Trautwine) Svo, 

Bovey's Treatise on Hydraulics iSvo, 

Church's Diagrams of Mean Velocity of Water in Open Channels. 

Oblong 4to . paper. 

Hydraulic Motors Svo, 

Mechanics of Engineering .Svo, 

Coffin's Graphical Solution of Hydraulic Problems. i6mo, mor. 

Flather's Dynamometers, and the Measurement of Power i2mo, 

Folwell's Water-supply Engineering Svo, 

Frizell's Water-power Svo, 

Fuertes's Water and Public Health i2mo. 

Water-filtration Works i2mo, 

Ganguillet and Kutter's General Formula for the Uniform Flow of Water in 

Rivers and Other Channels. (Hering and Trautwine j Svo, 

Hazen's Clean Water and How to Get It Large lamo, 

Filtration of Public Water-supplies Svo, 

Hazlehurst's Towers and Tanks for Water- works Svo, 

Herschel's 113 Experiments on the Carrying Capacity of Large, Riveted, Metal 

Conduits. Svo, 

Hoyt and Grover's River Discharge Svo, 

Hubbard and Kiersted's Water- works Management and Maintenance Svo, 

* Lyndon's Develop-nent and Electrical Distribution of Water ^ower. . . .Svo, 
Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 

Svo, 
Merriman's Treatise on Hydraulics Svo, 

* Michie's Elements of Analytical Mechanics Svo, 

* Molitor's Hvdraulics of Rivers. Weirs and Sluices 8vo, 

Richards's Laboratory Notes on Industrial Water Analysis. (In Press), 
Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- 
supply Large Svo, 

* Thoma- and Watt's Improvement of Rivers 4to, 

Tumeaure and Russell's Public Water-supplies Svo, 

Wegmann's Des'gn and Construction of Dams. 5th Ed., enlarged 4to, 

Water-supply of the City of New York from 165S to 1S95 4to, 10 00 

Whipple's Value of Pure Water Large i2mo, 

Williams and Hazen's Hydraulic Tables Svo. 

Wilson's Irr'ecat'on Engineering Small Svo, 

Wolff's Windmill as a Prime Mover Svo, 

Wood's Elements of Analytical Mechanics Svo, 

Turbines. Svo, 



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MATERIALS OF ENGINEERING. 



Baker's Roads and Pavements 8vo, 5 00 

Treatise on Masonry Construction 8vo, 5 00 

Birkmire's Architectural Iron and Steel 8vo, 3 50 

Compound Riveted Girders as Applied in Buildings Svo, 2 00 

Black's United States Public Works Oblong 4to. 5 00 

Bleininger's Manufacture of Hydraulic Cement. (In Preparation ) 

* Bovey's Strength of Materials and Theory of Structures Svo, 7 50 

Burr's Elasticity and Resistance of the Materials of Engineering Svo, 7 50 

Byrne's Highway Construction Svo, 5 00 

Inspection of the Materials and Workmanship Employed in Construction. 

i6mo, 3 00 

Church's Mechanics of Engineering Svo, 6 00 

Du Bois's Mechanics of Engineering. 

Vol. I. Kinematics, Statics, Kinetics Small 4to, 7 SO 

Vol. II. ihe Stresses in Framed Structures, Strength of Materi^-s a^^d 

Theory of Flexures Cmall 4to, 10 00 

♦Eckel's Cements, Limes, and Plasters Svo, 6 00 

Stone and Clay Products used in Engineering. (In Preparation.) 

Fowler's Ordinary Foundations Svo, 3 50 

Graves's Forest Mensuration Svo, 4 00 

Green's Principles of Americau Forestry i2mo, i 50 

* Greene's Structural Mechanics Svo, 2 50 

Holly and Ladd's Analysis of Mixed Paints, Color Pigments and Varnishes 

Large i2mo, 2 50 
Johnson's (C. M.) Chemical Analysis of Special Steels. (In Preparation.) 

Johnson's (J. B.) Materials of Construction Li.rge Svo, 6 00 

Keep's Cast Iron Svo, 2 50 

Kidder's Architecvs and Builders' Pocket-book i6mo, 5 00 

Lanza's Applied Mechanics Svo, 7 50 

Maire's Modern Pigments and their Vehicles l2mo, 2 00 

Martens's Handbook on Testing Materials. (Henning) 2 vols Svo, 7 50 

Maurer's Technical Mechanics Svo, 4 00 

Merrill's Stones for Building and Decoration Svo, 5 00 

Merriman's Mechanics of Materials Svo, 5 00 

* Strength of Materials lamo, i 00 

Metcalf's Steel. A Manual for Steel-users i2mo, 2 00 

Morrison's Highway Engineering 8vo, 2 50 

Patton's Practical Treatise on Foundations Svo, 5 00 

Rice's Concrete Flock Manufacture Svo, 2 Oq 

Richardson's Modern Asphalt Pavements Svo, 3 00 

Richey's Handbook for Superintendents of Construction i6mo, mor. 4 00 

* Ries's Clays: Their Occurrence, Properties, and Uses Svo, 5 00 

Sabin's Industrial and Artistic Technology of Paints ari Varnish Svo, 3 00 

*Schwar7,'sLon?1eaf Pine in Virgin Forest i?m^. i 25 

Snow's Principal Species of Wood 8vo, 3 50 

Spalding's Hydraulic Cement • i^mo, 2 00 

Text-book on Roads and Pavements i2mo, 2 00 

Taylor and Thompson's Treatise on Concrete, Plain and Reinforced Svo, 5 00 

Thurston's Materials of Engineering. In Three Parts Svo, 8 00 

Part I. Non-metallic Materials of Engineering and Metallurgy Svo, 2 00 

Part II. Iron and Steel ^^O' 3 50 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo, 2 50 

Tillson's Street Pavements and Paving Materials 8vo, 4 00 

Tumeaure and Maurer's Principles of Reinforced Concrete Construction.. .8vo, 3 00 

Waterbury's Cement Laboratory Manual i2mo, i 00 

9 



RAILWAY ENGINEERING. 

Andrews's Handbook for Street Railway Engineers 3x5 inches, mor. i 35 

Berg's Buildings and Structures of American Railroads 4to, 5 00 

Brooks's Handbook of Street Railroad Location i6mo, mor. z 50 

Butt's Civil Engineer's Field-book i6mo, mor. 3 50 

Crandall's Railway and Other Earthwork Tables . 8vo, i 50 

Transition Curve i6mo, mor. i 50 

* Crockett's Methods for Earthw^ork Computations 8vo, i 50 

Dawson's "Engineering" and Electric Traction Pocket-book i6mo. mor. 5 00 

Dredge's History of the Pennsylvania Railroad: (1879) Paper, 5 00 

Fisher's Table of Cubic Yards Cardboard, 25 

Godwin's Raihoad Engineers' Field-book and Explorers' Guide. . . i6mo, mor. 2 50 
Hudson's Tables for Calculating the Cubic Contents of Excavations and Em- 
bankments 8vo, 1 00 

Ives and Hilts's Problems in Surveying, Raihoad Surveying and Geodesy 

i6mo, mor. i 50 

Molitor and Beard's Manual for Resident Engineers i6nio, i 00 

Nagle's Field Manual for Raihoad Engineers i6mo, mor. 3 00 

Philbrick's Field Manual for Engineers i6mo, mor. 3 00 

Raymond's Railroad Engineering. 3 volumes. 

Vol. I. Railroad Field Geometry. (In Preparation.) 

Vol. II. Elements of Railraad Engineering 8vo, 3 50 

Vol III. Raihoad Engineer's Field Book. (In Preparation.) 

Searles's Field Engineering i6mo, mor. 3 00 

Raihoad Spiral i6mo, mor. i 50 

Taylor's Prismoidal Formulae and Earthwork 8vo, i 50 

*Trautwine's Field Practice of Laying Out Circular Curves for Raihoads. 

i2mo. mor, 2 50 

* Method of Calculating the Cubic Contents of Excavations and Embank- 

ments by the Aid of Diagrams 8vo, 2 00 

Webb's Economics of Raihoad Construction Large i2mo, 2 50 

Raihoad Construction i6mo, mor. 5 00 

Wellington's Economic Theory of the Location of Railways Small 8vo, 5 00 

DRAWING. 

Barr's Kinematics of Machinery 8vo, 

* Bartlett's Mechanical Drawing 8vo, 

* " " ♦• Abridged Ed 8vo, 

Coolidge's Manual of Drawing 8vo, paper, 

Coohdge and Freeman's Elements of General Drafting for Mechanical Engi- 
neers Oblong 4to, 

Durley's Kinematics of Machines 8vo, 

Emch's Introduction to Projective Geometry and its AppUcations 8vo, 

Hill's Text-book on Shades and Shadows, and Perspective 8vo, 

Jamison's Advanced Mechanical Drawing 8vo, 

Elements of Mechanical Drawing 8vo, 

Jones's Machine Design: 

Part I. Kinematics of Machinery 8vo, 

Part II. Form, Strength, and Proportions of Parts 8vo, 

MacCord's Elements of Descriptive Geometry 8vo, 

Kinematics ; or, Practical Mechanism 8vo, 

Mechanical Drawing 4to, 

Velocity Diagrams 8vo, 

McLeod's Descriptive Geometry Large i2mo, 

* Mahan's Descriptive Geometry and Stone-cutting 8vo, 

Industrial Drawing. (Thompson.) 8vo, 

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McLeod's Descriptive Geometry Large i2mo, 

* Mahan's Descriptive Geometry and Stone-cutting 8vo, 

Industrial Drawing. (Thompson ) 8vo, 

Moyer's Descriptive Geometry 8vo, 

Reed's Topographical Drawing and Sketching 4to, 

Reid's Course in Mechanical Drawing Svo, 

Text-book of Mechanical Drawing and Elementary Machine Design. Svo, 

Robinson's Principles of Mechanism Svo, 

Schwamb and Merrill's Elements of Mechanism Svo. 

Smith's (R. S.) Manual of Topographical Drawing. (McMillan) Svo, 

Smith (A. W.) and Marx's Machine Design Svo, 

* Titsworth's Elements of Mechanical Drawing Oblong Svo, 

Warren's Drafting Instruments and Operations 12 mo. 

Elements of Descriptive Geometry, Shadows, and Perspective Svo, 

Elements of Machine Construction and Drawing Svo, 

Elements of Plane and Solid Free-hand Geometrical Drawing i2mo, 

General Problems of Shades and Shadows Svo, 

Manual of Elementary Problems in the Linear Perspective of Form and 

Shadow i2mo. 

Manual of Elementary Projection Drawing. , i2mo. 

Plane Problems in Elementary Geometry i2mo. 

Problems, Theorems, and Examples in Descriptive Geometry Svo, 

Weisbach's Kinematics and Power of Transmission. (Hermann and 
Klein) Svo, 

Wilson's (H. M.) Topographic Surveying Svo, 

Wilson's (V. T.) Free-hand Lettering. . , Svo, 

Free-hand Perspective Svo, 

Woolf' s Elementary Course in Descriptive Geometry^ Large Svo. 

ELECTRICITY AND PHYSICS. 

* Abegg's Theory of Electrolytic Dissociation, (von Ende) i2mo. 

Andrews's Hand-Book for Street Railway Engineering. ... .3X5 inches, mor. 

Anthony and Brackett's Text-book of Physics. (Magie) Large i2mo, 

Anthony's Theory of Electrical Measurements. (Ball) i2mo, 

Benjamin's History of Electricity Svo, 

Voltaic CeU Svo, 

Betts's Lead Refining and Electrolysis Svo, 

Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood)..8vo, 

* Collins's Manual of Wireless Telegraphy.. i2mo, 

Mor. 
Crehore and Squier's Polarizing Photo-chronograph Svo, 

* Danneel's Electrochemistry. (Merriam) i2mo, 

Dawson's "Engineering" and Electric Traction Pocket-book .... i6mo, mor. 

Dolezalek's Theoryof the Lead Accumulator (Storage Battery), (von Ende) 

i2mo, 

Duhem's Thermodynamics and Chemistry. (Burgess) Svo, 

Flather's Dynamometers, and the Measurement of Power i2mo, 

Gilbert's De Magnete. (Mottelay) Svo, 

* Hanchett's Alternating Currents i2mo, 

Bering's Ready Reference Tables (Conversion Factors') i6mo, mor. 

* Hobart and Ellis's Hi?h-speed Dynamo Electric Machinery Svo, 

Holman's Precision of Measurements. Svo, 

Telescopic Mirror-scale Method, Adjustments, and Tests. . . .Large Svc, 

* Karapetoff' s Experimental Electrical Engineering 8vo, 

Kinzbrunner's Testing of Continuous-current Machines Svo, 

Landau^r's Spectrum Analysis. (Tingle) Svo, 

Le Chatpher's High-temperature Measurements. (Boudouard— Burgess )..i2mo. 
Lob's Electrochemistry of Organic Compounds. (Lorenz) Svo, 

* Lyndon's Development and Electrical Distribution of Water Power Svo, 

11 



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* Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and 11. 8vo, each 

* Michie's Elements of Wave Motion Relating to Sound and Light 8vo, 

Morgan's Outline of the Theory of Solution and its Results zamo, 

* Physical Chemistry for Electrical Engineers lamo, 

Niaudet's Elementary Treatise on Electric Batteries. (Fishback) zamo, 

* Norris's Introduction to the Study of Electrical Engineering 8vo, 

* Parshall and Hobart's Electric Machine Design 4to, half mor. 

Reagan's Locomotives: Simple, Compound, and Electric. New Edition. 

Large 12 mo, 

* Rosenberg's Electrical Engineering. (Haldane Gee — Kinzbrunner) . . .8vo, 

Ryan, Norris, and Hoxie's Electrical Machinery. Vol. I 8vo, 

Schapper's Laboratory Guide for Students in Physical Chemistry zamo, 

* Tillman's Elementary Lessons in Heat 8vo, 

Tory and Pitcher's Manual of Laboratory Physics Large zamo. 

Ulke's Modern Electrolytic Copper Refining 8vo, 

LAW. 

Brennan's Handbook: A Compendium of Useful Legal Information for 
Business Men : z6mo, mor. 

* Davis's Elements of Law 8vo, 

* Treatise on the Military Law of United States 8vo, 

* Sheep, 

* Dudley's Military Law and the Procedure of Courts-martial. . .Large zamo. 

Manual for Courts-martial z6mo, mor. 

Wait's Engineering and Architectural Jurisprudence 8vo, 

Sheep, 

Law of Contracts 8 vo. 

Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture 8 vo. 

Sheep, 

MATHEMATICS. 

Baker's Elliptic Functions 8vo, 

Briggs's Elements of Plane Analytic Geometry. (Bocher) zamo» 

* Buchanan's Plane and Spherical Trigonometry 8vo, 

Byerley's Harmonic Functions 8vo, 

Chandler's Elements of the Infinitesimal Calculus lamo. 

Coffin's Vector Analysis. (In Press.) 

Compton's Manual of Logarithmic Computations zamo, 

* Dickson's College Algebra Large lamo, 

* Introduction to the Theory of Algebraic Equations Large zamo, 

Emch's Introduction to Projective Geometry and its Applications .8vo, 

Fiske's Functions of a Complex Variable 8vo, 

Halsted's Elementary Synthetic Geometry 8vo, 

Elements of Geometry 8vo, 

* Rational Geometry zamo, 

Hyde's Grassmann's Space Analysis 8vo, 

♦Johnson's (J. B.) Three-place Logarithmic Tables: Vest-pocket size, paper, 

zoo copies, 

* Mounted on heavy cardboard, 8 X zo inches, 

zo copies, 
Johnson's (W. W.) Abridged Editions of Differential and Integral Calculus 

Large zamo. z vol. 

Curve Tracing in Cartesian Co-ordinates zamo. 

Differential Equations 8vo, 

Elementary Treatise on Differential Calculus Large zamo. 

Elementary Treatise on the Integral Calculus Large zamo. 

Theoretical Mechanics zamo. 

Theory of Errors and the Method of Least Squares zamo. 

Treatise on Differential Calculus Large zamo, 

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Johnson's Treatise on the Integral Calculus Large i2mo, 3 00 

Treatise on Ordinary and Partial Differential Equations. . Large i2mo, 3 50 
£arapetofC's Engineering Applications of Higher Mathematics. (In Pre- 
paration.) 
Laplace's Philosophical Essay on Probabilities. (Truscott and Emory). .i2mo, 2 00 

* Ludlow and Bass's Elements of Trigonometry and Logarithmic and Other 

Tables 8vo, j 00 

Trigonometry and Tables published separately Each, 2 00 

* Ludlow's Logarithmic and Trigonometric Tables 8vo, i 00 

Macfarlane's Vector Analysis and Quaternions 8vo, i 00 

McManon's Hyperbolic Functions Svo, i 00 

Manning's Irrational Clumbers and their Representation by Sequences and 

Series i2mo, i 2S 

Mathematical Monographs. Edited by Mansfield Merriman and Robert 

S. Woodward Octavo, each i 00 

No. I. History of Modern Mathematics, by David Eugene Smith. 
No. 2. Synthetic Projective Geometry, by George Bruce Halsted. 
No. 3. Determinants, by Laenas Gifford Weld. No. 4. Hyper- 
bolic Functions, by James McMahon. Ko. 5. Harmonic Func- 
tions, by William E. Byerly. No. 6. Grassmann's Space Analysis, 
by Edward W, Hyde. No. 7. Probability and Theory of Errors, 
by Robert S. Woodward. No. 8. Vector Analysis and Quaternions, 
by Alexander Macfarlane. No. 9. Differential Equations, by 
William Woolsey Johnson. No. 10. The Solution of Equations, 
by Mansfield Merriman. No. 11. Functions of a Complex Variable, 
by Thomas S. Fiske. 

Maurer's Technical Mechanics Svo, 4 00 

Merriman's Method of Least Squares Svo, 2 00 

Solution of Equations Svo, I 00 

Rice and Johnson's Differential and Integral Calculus. 2 vols, in one. 

Large i2mo, i 50 

Elementary Treatise on the Differential Calculus Large i2mo, 3 00 

Smith's History of Modern Mathematics Svo, i 00 

* Veblen and Lennes's Introduction to the Real Infinitesimal Analysis of One 

Variable Svo, 2 00 

* Waterbury's Vest Pocket Hand-Book of Mathematics for Engineers. 

2 8"X58 inches, mor. i 00 

Weld's Determinations Svo, i 00 

Wood's Elements of Co-ordinate Geometry Svo, 2 00 

Woodward's Probability aid Theory of Errors 8vo, i oo 

MECHANICAL ENGINEERING. 

MATERIALS OF ENGINEERING, STEAM-ENGINES AND BOILERS. 

Bacon's Forge Practice i2mo, i 50 

Baldwin's Steam Heating for Buildings i2mo, 2 50 

Bair's Kinematics of Machinery Svo, 2 50 

* Bartlett's Mechanical Drawing Svo, 3 00 

* " " " Abridged Ed Svo, 150 

Benjamin's Wrinkles and Recipes i2mo, 2 00 

* Burr's Ar ci3nt and Modern Engineering and the Isthmian Canal Svo, 3 50 

Carpenter's Experimental Engineering Svo, 6 00 

Heating and Ventilating Buildings Svo, 4 00 

Clerk's Gas and Oil Engine Large i2mo, 4 00 

Compton's First Lessons in Metal Working i2mo, i 50 

Compton and De Groodt's Speed Lathe i2mo, i 50 

CooUdge's Manual of Drawing Svo, paper, i 00 

Coolidge and Freeman's Elements of General Drafting for Mechanical En- 
gineers Oblong 4to, 2 50 

13 



Cromwell's Treatise on Belts and Pulleys i2mo, 

Treatise on Toothed Gearing i2mo, 

Durley's Kinematics of Machines 8vo, 

Flather's Dynamometers and the Measurement of Power i2mo, 

Rope Driving i2mo. 

Gill's Gas and Fuel Analysis for Engineers , i2mo, 

Goss s L'^comotive Sparks 8vo, 

Greene's Pumping Machinery. (In Preparation.) 

Bering's Ready Reference Tables (Conversion Factors) i6mo, mor. 

* Hobart and Ellis's High Speed Dynamo Electric Machinery 8vo, 

Button's Gas Engine 8vo, 

Jamison's Advanced Mechanical Drawing 8vo, 

Elements of Mechanical Drawing 8vo, 

Jones's Gas Engine. (In Press.) 
Machine Design: 

Part I. Kinematics of Machinery 8vo, 

Part II. Form, Strength, and Proportions of Parts 8vo, 

Kent's Mechanical Engineers' Pocket-book i6mo, mor. 

Kerr's Power and Power Transmission 8vo, 

Leonard's Machine Shop Tools and Methods 8vo, 

* Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean) . . . 8vo, 
MacCord's Kinematics; or. Practical Mechanism 8vo, 

Mechanical Drawing 4to, 

Velocity Diagrams 8vo, 

MacFarland's Standard Reduction Factors for Gases 8vo, 

Mahan's Industrial Drawing. (Thompson) 8vo, 

Oberg's Screw Thread Systems, Taps, Dies, Cutters, and Reamers. (In 
Press.) 

* Parshall and Hobart's Electric Machine Design Small 4to, half leather, 

Peele's Compressed Air Plant for Mines 8vo, 

Poole's Calorific Power of Fuels 8vo, 

* Porter's Engineering Reminiscences, 1855 to 1882 8vo, 

Reid's Course in Mechanical Drawing 8vo, 

Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 

Richard's Compressed Air i2mo, 

Robinson's Principles of Mechanism 8vo, 

Schwamb and Merrill's Elements of Mechanism 8vo, 

Smith's (0.) Press- working of Metals 8vo, 

Smith (A. W.) and Marx's Machine Design 8vo, 

Sore! ' s Carbureting and Combustion in Alcohol Engines . (Woodward and Preston) . 

Large 12 mo, 

Thurston's Animal as a Machine and Prime Motor, and the Laws of Energetics. 

i2mo. 

Treatise on Friction and Lost Work in Machinery and Mill Work... 8vo, 

Tillson's Complete Automobile Instructor i6mo, 

mor. 

Titsworth's Elements of Mechanical Drawing Oblong 8vo, 

Warren's Elements of Machine Construction and Drawing 8vo, 

* Waterbury's Vest Pocket Hand Book of Mathematics for Engineers. 

2JX5I- inches, mor. 
Weisbach's Kinematics and the Power of Transmission. (Herrmann — 

Klein) 8vo, 

Machinery of Transmission and Governors. (Herrmann — Klein). . . 8vo, 
Wood's Turbines - 8vo, 

MATERIALS OF ENGINEERING 

* Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 

Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 50 

Church's Mechanics of Engineering 8vo, 6 00 

* Greene's Structural Mechanics 8vo, 2 50 

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HoUey and Ladd's Analysis of Mixed Paints, Color Pigments, and Varnishes. 

' Large lamo, 2 50 

Johnson's Materials of Construction g^°' ^ °° 

Keep's Cast Iron g ' 

Lanza's Applied Mechamcs 

Maire's Modern Pigments and their Vehicles i^mo, 2 00 

Martens's Handbook on Testing Materials. (Henning) «vo, 7 5o 

Maurer's Technical Mechanics ^°' ^^ 

Merriman's Mechanics of Materials ' ^ 

.,_,.., i2mo, I 00 

* Strength of Materials 

Metcalf's Steel. A Manual for Steel-users. . . ^^ ^ " . •. ^""T" \ °° 

Sabin's Industrial and Artistic Technology of Pamts and Varnish 8vQ, 3 00 

. . , -.r 1 • . . .i2mo. I 00 

Smith's Materials of Machines 

Thurston's Materials of Engineering • • • • • -3 vols., 8vo, 8 00 

Part 1 Non-metallic Materials of Engineering and Metallurgy . . . Svo. 2 00 

Part II. Iron and Steel • • ; - fj"".^ ^ ^o 

Part III A Treatise on Brasses, Bronzes, and Other Alloys and their 

": ' ., ^ Svo, 250 

Constituents 

Wood's (De V.) Elements of Analytical Mechanics ;: ' ' " 1°' ^ 

Treatise on the Resistance of Materials and an Appendix on the 

Preservation of Timber ■,■■.■■■■,■■■ I 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of I^on and 

Steel 



• STEAM-ENGINES AND BOILERS. 

Berry's Temperature-entropy Diagram • i2mo, i 25 

Carnot's Reflections on the Motive Power of Heat. (Thurston) i2mo. i 50 

Chase's Art of Pattern Making " ' ^ 

Creiehton's Ste im-engine and other Heat-motors • »vo, 5 «" 

Dawson's " Engineering" and Electric Traction Pocket-book i6mo, mor. 5 00 

Ford's Boiler Making for Boiler Makers 1°°^°' ^ ° 

♦ Gebhardt's Steam Power Plant Engineering »JO' 

. ^ r 8vo, 5 00 

Goss's Locomotive Performance nn 

Hemenway's Indicator Practice and Steam-engine Economy i2mo, 2 00 

Button's Heat and Heat-engines ^°' 

Mechanical Engineering of Power Plants °^0' 5 00 

Kent's Steam boiler Economy ^°' ^ 

Kneass's Practice and Theory of the Injector »vo, i 50 

, oVOt 2 00 

MacCord's Shde-valves • 

Meyer's Modern Locomotive Construction 4^°' ' 

Moyer's Steam Turbines. (Tn Press.) 

Peabody's Manual of the Steam-engine Indicator i2mo. i 50 

Tables of the Properties of Saturated Steam and Other Vapors 8vo. i 00 

Thermodynamics of the Steam-engine and Other Heat-engines 8vo, 5 00 

Valve-gears for Steam-engines °^°' ^ ^o 

Peabody and Miller's Steam-boilers • °^°' 4 00 

Pray's Twenty Years with the Indicator 1-arge »vo, 2 50 

Puoin's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors. 

^ /.-. X u ^ i2mo, 1 2< 

(Osterberg:) • • ■ • • ; » 

Reagan's Locomotives. Simple, Compound, and Electric. New Edition. 

Large i2mo, 3 50 

Sinclair's Locomotive Engine Running and Management i2mo, 2 00 

Smart's Handbook of Engineering Laboratory Practice i2mo, 2 50 

Snow's Steam-boiler Practice ^^°' ^ 00 

Soangler's Notes on Thermodynamics ""^o- ^ °° 

^ „ , Svo, 2 50 

Valve-gears • - ; ' _ 

Spangler, Greene, and Marshall's Elements of Steam-engineenng 8vo, 3 00 

Thomas's Steam-turbines ^^°' "* °^ 

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Thurston's Handbook of Engine and Boiler Trials, and the Use of the Indi- 
cator and the Prony Brake £vo, 5 00 

Handy Tables 8vo, i 50 

Manual of Stram-boilers, their resigns. Construction, and Operation.. 8vo, 5 00 

Thurston's Manual of the Steam-engine 2 vols., 8vo, 10 00 

Part I. History, Structure, and Theory 8v^, 

Part n. Design, Construction, and Operation 8vo, 

Steam-boiler Explosions in Theory and in Practice i2mo, 

Wehrenfenning's Analysis and Softening of Boiler Feed-water (Patterson) 8vo, 

Weisbach's Heat, Steam, and Steam-engines. (Du Bois) 8vo, 

TVhitham's Steam-engine Design 8vo, 

Wood's Thermodynamics, Heat Motors, and Refrigerating Machines. . .8vo, 

MECHANICS PURE AND APPLIED. 

Church's Mechanics of Engineering 8vo, 

Notes and Examples in Mechanics 8vo, 

Dam's Text-boofc of Elementary Mechanics for Colleges and Schools. .i2mo» 
Du Bois's Elementary Principles of Mechanics: 

Vol. I. Kinematics 8vo, 

Vol. n. Statics 8vo, 

Mechanics of Engineering. Vol. I Small 4to, 

VoL n. Small 4to, 10 00 

* Greene's Structural Mechanics Svo, 2 50 

James's Kinematics of a Point and the Rational Mechanics of a Particle. 

Large i2mo, 

* Johnson's (W. W.) Theoretical Mechanics i2mo. 

Lanza's Applied Mechanics Svo, 

* Martin's Text Book on Mechanics, Vol. I, Statics i2mo, 

* Vol. 2, Kinematics and Kinetics . .i2mo, 
Maurer's Technical Mechanics Svo, 

* Merriman's Elements of Mechanics* i2mo. 

Mechanics of Materials Svo, 

* Michie's Elements of Analytical Mechanics Svo, 

Robinson's Principles of Mechanism Svo, 

Sanborn's Mechanics Problems Large i2mo, 

Schwamb and Merrill's Elements of Mechanism Svo, 

Wood's Elements of Analytical Mechanics Cvo, 

Principles of Elementary Mechanics i2mo, 

MEDICAL. 

* Abderhalden's Physiological Chemistry in Thirty Lectures. (Hall and Defren) 

Svo, 
von Behring's Suppression of Tuberculosis. (Bolduan) i2mo, 

* Bolduan's Immune Sera i2mo, 

Bordet s Contribution to Immunity. (Gay). (In Preparation.) 
Davenport's Statis ical Methods with Special Reference to Biological Varia- 
tions i6mo, mor. 

Ehrlich's Collected Studies on Immunity. (Bolduan) Svo, 

* Fischer's Physiology of AUmentation Large i2mo, cloth, 

de Fursac's Manual of Psychiatry. (Rosanoff and Collins) Large i2mo, 

Hammarsten's Text-book on Physiological Chemistry. (Mandel) .8vo, 

Jackson's Directions for Laboratory Work in Physiological Chemistry. ..Svo, 

Lassar-Cohn's Practical Urinary Analysis. (Lorenz) i2mo, 

Mandel's Hand Book for the Bi -Chemical Laboratory i2mo, 

* PauU's Physical Chemistry in the Service of Medicine. (Fischer) i2mo, 

* Pozzi-Escot's Toxins and Venoms and their Antibodies. (Cohn) i2mo, 

Rostoski's Serum Diagnosis. (Bolduan) i2mo, 

Ruddiman's Incompatibilities in Prescriptions 8vo, 

Whys in Pharmacy i2mo, 

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Salkowski's Physiological and Pathological Chemistry. (Orndorff) 8vo, 2 50 

* Satterlee's Outlines of Human Embryology i2nio. 1 25 

Smith's Lecture Notes on Chemistry for Dental Students 8vo , 2 50 

Steel's Treatise on the Diseases of the Dog . , 8vo, 3 50 

* Whipple's Typhoid Fever Large i2mo, 3 00 

Woodhull's Notes on Military Hygiene . . . : i6mo, 1 50 

* Personal Hygiene i2mo, i 00 

Worcester and Atkinson's Small Hospitals Establishment and Maintenance, 

and S ggestions for Hospital Architecture, with Plans for a Small 

Hospital i2mo, z 25 

METALLURGY. 

Betts's Lead Refining by Electrolysis 8vo, 4 00 

BoUand's Encyclopedia of Founding and Dictionary of Foundry Terms Used 

in the Practice of Moulding i2mo. 

Iron Founder . , i2mo, 

" " Supplement i2mo, 

Douglas's Untechnical Addresses on Tfchnical Subjects i2mo, 

Goesel's Minerals and Metals: A Reference Book ,- i6mo, mor. 

* Iles's Lead-smelting i2mo, 

Keep's Cast Iron 8vo, 

Le Chatelier's High-temperature Measurements. (Boudouard — Burgess) 1 2mo, 

Metcalf s Steel. A Manual for Steel-users i2mo. 

Miller's Cyanide Process i2mo, 

Minet's Production of Aluminium and its Industrial Use. (Waldo) . . .i2mo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc) 8vo, 

Ruer's Elements of Metallography. (Mathewson) (In Press.) 

Smith's Materials of Machines i2mo, 

Tate and Stone's Foundry Practice. (In Press.) 

Thurston's Materials of Engineering. In Three Parts . 8vo, 

Part I. Non-metallic Materials of Engineering and Metallurgy . . . 8vo, 

Part n. Iron and Steel Svo, 

Part in. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents Svo, 

Ulke's Modern Electrolytic Copper Refining Svo, 

Wesfs American Foundry Practice i2mo. 

Moulder's Text Book i2mo, 

Wilson's Chlorination Process i2mo. 

Cyanide Processes i2mo, 

MINERALOGY. 

Barringer's Descripti'^n of Minerals of Commercial Value Oblong, mor. 2 50 

Boyd's Resources of Southwest Virginia Svo, 3 00 

B»yd's Map of Southwest Virginia Pocket-book form. 2 00 

* Browning's Introduction to the Rarer Elements 8vo, i 50 

Brush's Manual of Determinative Mineralogy. (Penfield) Svo, 4 00 

Butler's Pocket Hand-Book of Minerals i6mo, mor. 3 00 

Chester's Catalogue of Minerals Svo, paper, i 00 

Cloth, I 25 

* Crane*s Gold and Silver Svo, 5 00 

Dana's First Appendix to Dana's New "System of Mineralogy..". .Large Svo, i 00 

Manual of Mineralogy and Petrography ^ i2mo 2 00 

Minerals and How to Study Them i2mo, 1 50 

System of Mineralogy Large Svo, half leather, 12 50 

Text-book of Mineralogy. Svo, 4 00 

Douglas's Untechnical Addresses on Technical Subjects i2mo, i 00 

Eakle's Mineral Tables Svo, i 25 

Stone and Clay Products Used in Engineering. (In Preparation.) 

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Egleston's Catalogue of Minerals and Synonyms 8vo, 

Goesel's Minerals and Metals : A Reference Book i6mo mor, 

Groth's Introduction to Chemical Crystallography (Marshall) i2mo, 

* Iddmgs's Rock Minerals . 8vo, 

Johannsen's Determination of Rock-forming Minerals in Thin Sections 8vo, 

* Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe. l2mo, 
Merrill's Non-metallic Minerals: Iheir Occurrence and Uses 8vo, 

Stones for Buildinsr and Decoration Svo, 

* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 

Svo, paper, so 
Tables of Minerals, Including the Use of Minerals and Statistics of 

Domestic Production Svo, i oo 

* Pirsson's Rocks and Rock Minerals . i2mo, 2 50 

* Richards's Synopsis ot Mineral Characters i2mo, mor. i 25 

* Ries's Clays: Their Occurrence Properties, and Uses Svo, 5 00 

* Tillman's Text-book of Important Minerals and Rocks Svo, 2 00 

MININa 

"* Beard's Mine Gases and Explosions Large i2mo, 

Boyd's Map of Southwest Viiginia Pocket-oook rorm. 

Resources of Southwest Virginia Svo, 

* Crane's Gold and Silver Svo, 

Douglas's Untechnical Addresses on Technical Subjects i2mo 

Eissler's Modern High Explosives Svo, 

Goesel's Minerals and Metals : A Reference Book i6mo, mor. 

l! Iseng's Manual of Mining Svo, 

* Ues's Lead-smelting i2mo, 

Miller's Cyanide Process i2mo, 

O'DriscoJl's Notes on the Treatment of Gold Ores Svo, 

Peele's Compressed Air Plant for Mines Svo, 

Riemer's Shaft Sinking Under Difficult Conditions. (Coming and Peele) . . .8vo, 
Robine and Lenglen's Cyanide Industry. (Le Clerc) Svo, 

* Weaver's Military Explosives Svo, 

Wilson's Chlorination Process i2mo. 

Cyanide Processes i2mo, 

Hydraulic and Pldcer Mining. 2d edition, rewritten i2mo, 

Treatise on Practical and Theoretical Mine Ventilation T2mo, 

SANITARY SCIENCE. 

Association of State and National Food and Dairy Departments, Hartford Meeting, 

1 906 Svo, 

Jamestown Meeting, 1907 Svo, 

* Bashore's Outlines of Practical 'Sanitation i2mo, 

Sanitation ot a Country House i2mo. 

Sanitation of Recreation Camps and Parks i2mo, 

Folwell's Sewerage. (Designing, Construction, and Maintenance) Svo, 

Water-supply Engineering Svo, 

Fowler's Sewage Works Analyses i2mo, 

Fuertes's Water-filtration Works i2mo. 

Water and Public Health i2mo, 

Gerhard's Guide to Sanitary House-inspection i6mo, 

* Modem Baths and Bath Houses Svo, 

Sanitation of Public Buildings = i2mo, 

Hazen's Clean Water and How to Get It Large i2mo. 

Filtration of Public Water-suppHes Svo, 

Kinnicut, Winslow and Pratt's Purification of Sewage. (In Press.) 

Leach's Inspection and Analysis of Food with Special Reference to State 

Control Svo, 7 00 

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Mason's Examination of Water. (Chemical and Bacteriological) i2mo. 

Water-supply. (Considered Principally from a Sanitary Standpoint) . .8vo, 

* Merriman's Elements of Sanitary Engineering 8vo, 

Ogden's Sewer Design i2mo, 

Parsons's Disposal of Municipal Refuse 8vo, 

Prescott and WinsloWb Elements of Water Bacteriology, with Special Refer- 
ence to Sanitary Water Analysis i2mo, 

* Price's Handbook on Sanitation i2mo, 

Richards's Cost of Cleanness. A Twentieth Century Problem i2mo, 

Cost ot tood. A Study in Dietaries i2mo, 

Cost of Living as Modified by Sanitary Science. i2mo, 

Cost of Shelter. A Study in Economics i2mo, 

* Richards and Williams's Dietary Computer 8vo, 

Richards and Woodman's Air, Water, and Food from a Sanitary Stand- 
point 8vo, 

Rideal's Disinfection and the Preservation of Food 8vo, 

Sewage and Bacterial Purification of Sewage 8vo, 

Sopor's Air and Ventilation of Subways . Large i2mo, 

Turneaure and Rus«;eirs Public Water-supplies 8vo, 

Venable's Garbage Crematories in America 8vo, 

Method and Devices for Bacterial Treatment of Sewage 8vo, 

Ward and Whipple's Freshwater Biology i2too, 

Whipple's Microscopy of Drinking-water 8vo, 

* T^phod Fever Large 1 2mo, 

Value of Pure Water Large 1 2mo, 

Winslow's Bacterial Classification i2mo, 

Winton's Microscopy of Vegetable Foods 8vo, 

MISCELLANEOUS. 

Emmons's Geological Guide-book of the Rocky Mountain Excursion of the 

Inter ational Congress of Geologists Large 8vo, 

Ferrel's Popular Treatise on the Winds. . , 8vo, 

Fitzgerald's Boston Machinist i8mo, 

Gannett's Statistical Abstract of the World 24mo, 

Haines's American Railway Management i2mo, 

* Hanusek's The Microscopy of Technical Products. (Winton) 8vo, 

Owen's The Dyeing and Cleaning of Textile Fabrics. (Standage ). (In Press.) 
Ricketts's History of Rensselaer Polytechnic Institute 1824-1894. 

Large i2mo, 

Rotherham's Emphasized New Testament ^ Large 8yo, 

Standage's Decoration of Wood, Glass, Metal, etc i2mo, 

Thome's Structural and Physiological Botany. (Bennett) i6mo, 

Westermaier's Compendium of General Botany, (Schneider) 8vo, 

Winslow's Elements of Applied Microscopy i2mo, 



HEBREW AND CHALDEE TEXT-BOOKS. 

Green's Elementary Hebrew Grammar lamo, t 25 

Gesenius's Hebrew and Chaldee Lexicon to the Old Testament Scriptures. 

(Tregelles) Small 4to, half mor. s 00 

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